I use the Quadcurve EQ most if not all of the time. One big reason is in Platinum it has the very cool flyout display. If one has not seen or used it, I can see why one may want something more user friendly. I have all the modules for Pro Channel with a few third party ones. Understanding the power of the PC is not easily explained. Though Professional comes with the PC it does not include all the modules that come with Platinum. If you look around you'l find that Sonar was the first to have a channel strip but others have seen how good and useful it can be and have tried to copied it. However none is as good or as versatile as the one in Platinum because it is customizable.  
 
My view is that CW has never bundled poor quality plugins. I can name developers that have. If one is thinking because it comes with the program it can't be as good as a third party version you would be mistaken. I will amend my above statement to add that the only plugin I would count as not up to the quality that CW has always adhered to is Boost 11. Still many use and like it. But in fairness it was not meant for Platinum or the old Producer where it first appeared in Sonar. It was asked for by some vocal members when they saw it in Home Studio. CW added it because enough saw it and wanted it.   
 
Really I can't see how one can go wrong getting the top flagship version where CW puts all it expertise.  
 
With it one also gets lifetime updates. That alone should be the clincher.  

Arizona

Anderton
 
Closer to home, the different curves on the QuadCurve can make a huge difference. If you know how to use the functionality, you'll get a better sound...but that doesn't mean anyone will know how you got that sound.

@Anderton,
 
I think you're saying that there are two useful but independent attributes:
1) The sound quality of the processor
2) The functionality and user interface that make it easy to use the processor effectively
 
I think you're implying that the QuadCurve's sound quality is up to industry standards, but the functionality and user interface are what makes the QuadCurve exceptional.
 
Is that what you mean?
 

Yes, but of course with the caveat of exceptional for me. The reason why is I've learned what all the curves do, so I know which one to call up for a given application. The QuadCurve is already in the ProChannel...a couple clicks, done.
 
But really, this whole discussion of what's "better" or "best" does not lend itself to generalizations very well. If a track needs a 1.7 dB lift with a fairly wide bandwidth at 3.5 kHz, I defy anyone to tell the difference between just about any plug-in EQ made since 2005. However reverbs have very different sonic signatures because a) reverb is hellishly difficult to do, and b) different designers have different ideas of what sounds "good." For example Breverb does an excellent job of imitating old-school algorithmic reverbs and some people covet that sound. Softube's TSAR-1 is a much more transparent reverb that almost sounds synthetic, which I love for some applications. Which one is better? Depends on how you want to use them. 
 
I also think it's important to distinguish between what sounds "better" and what sounds "different." Again using reverb as an example, the early 12-bit hardware digital reverbs sounded grainy and coarse. To me just about any modern reverb sounds better. But is modern reverb A "better" or "different" than modern reverb B?
 
I agree with pwalpwal that if you've been around the block and have a lot of plug-ins, most if not all of the plug-ins in SONAR would be redundant. With a few exceptions they're clearly designed to give what's essential, not what's esoteric. However I don't agree that "long in the tooth" is an inherent problem. In the original post, I found it humorous that someone would say a synth is "outdated" when the standard of comparison many use to judge the quality of a virtual instrument is how close it can come to a 1972 Minimoog .
 
For example consider the Sonitus Delay. Despite having accumulated over 2,000 plug-ins over the years, I don't have anything that can do what the Sonitus does. But I also don't have anything that can do what the PSP Audioware 608 Multidelay can do, either. Similarly, I did an exact model of a Vox Clyde McCoy wah using the Sonitus Wah. Nothing else has come close other than models in amp sims.
 
I truly think plug-ins have very little do with the emotional impact of a piece of music on the listener, and here I agree with sanderxpander on the importance of the interface. If you can dial in the sound you want in seconds and maintain your creative flow, your music will have more emotional impact than if you spend time dialing in a "perfect" sound but lose your creative impulse in the process.
 
Because a lot of my projects have hard and unforgiving deadlines, I use SONAR's plug-ins much more than any others because they're fast, have excellent sound quality, and I know how to get the sounds I want. FWIW no client has ever said "Y'know, it sounds like you're using bundled plug-ins. You really should be using more expensive third-party stuff."
 
 

One final plug-in story.
 
Sound on Sound magazine does a feature called "Mix Rescue" where they go to a reader's house and assist with a mix. They arrived at their host's, who went to make tea for them. While he was doing that, they bypassed all the plug-ins to hear what the raw tracks sounded like.
 
When the host came back to the studio with the tea, he said "Wow! That sounds so much better!! What did you guys do?!?"

I remember that story Graig. Its one we should all take to heart. 

We had the exact same thing happen on the forum, someone came in and said "after working on my mix for a few hours I hit 'E' and suddenly everything sounded much better... What does 'E' do?" :)

If Pro Audio 9 was the last DAW you played with, I think you'd be happier with Studio One 3.
 

Pro to Plat? I never really thought twice, never looked back. Splat with lifetime updates as well as platinum exclusives, well worth the price. Money well spent! 

Thanks to everyone for your comments and advice. To summarize so far, the most popular plugins include:
 
Exclusive to Sonar Platinum:

• Addictive Drums 2 (This is the only specific instrument plugin mentioned.)
• BiFilter 2
• Breverb
• Console Emulator
• Drum Replacer
• PX-64 Percussion Strip
• QuadCurve EQ with zoom spectrum analysis
• S-Type Bus Compressor
• Theme Editor
• TS-64 Transient Shaper
• VocalSync
• VX-64 Vocal Strip

On the other hand, some prefer 3rd party plugins. 
 
Other favorites, not exclusive to Platinum:

• LP EQ linear phase equalizer (Platinum and Professional)
• Melodyne (Platinum and Professional)
• Nomad Factory Blue Tubes bundle (Platinum and Professional)
• REmatrix Solo (Platinum and Professional)
• Softube's TSAR 1 -- Not clear whether this is included with Sonar Platinum
• Sonitus bundle (Included in all current versions of Sonar)

 
Reference
cakewalk.com/Products/SONAR/Versions
cakewalk.com/Documentation?product=SONAR&language=3&help=Plug-ins.1.html
 
This is all very helpful. Thanks!
Of course, further comments are welcome, whether you use Sonar plugins or prefer 3rd party plugins.
 
[Edited]

Arizona

I'm trying to decide which version of Cakewalk Sonar to purchase. I've looked at the comparison chart here:
www.cakewalk.com/Products/SONAR/Versions#start

And I've looked at the plugins list here:
www.cakewalk.com/Documentation?product=SONAR&language=3&help=Plug-ins.1.html

Those pages are helpful, but Platinum's extra features do not represent benefits to me, because I've never used them. Hence, I'm not familiar with them, and I don't know how useful they are. Also, I've read somewhere that some of Platinum's virtual instruments sound a bit out-dated, in one reviewer's opinion.

So, I'm hoping to hear some personal opinions about which particular features in Platinum make it worth the extra money. (E.g. True Pianos? Or Lounge Lizard?) Alternatively, why is Sonar Professional sufficient for you? Please tell me why you yourself chose either Professional or Platinum. Are you happy with your choice?

By the way, I stopped using DAW software at Cakewalk Pro Audio 9 and Samplitude 6, so I'm a total newb with Sonar. I'm on Windows 8.1 with an Intel i7 Skylake processor, and about 32 GB RAM.

So I'm guessing that you don't have a rack of modern effect plugins and virtual instruments?  Get Platinum.

For one, the lifetime updates assures that you will have a DAW that keeps up with whatever Microsoft does to Windows in the future.  That could be huuuuuge!

Then the included effects and instruments should be fine to get you back up to date.  They don't suck.  You could spend hundreds, or even thousands, on software plugs to get a setup you like, ala carte.

Just so you know, my opinion is based on someone who doesn't make a living with this stuff.  I am a music hobbyist who has been using music technology since the 80's. My first keyboard synth choice was between a Roland Juno xx-something, and the keyboard I ended up with.  Should have picked the Juno, LOL!

The first computer sequencer I saw was an Apple Mac demo at the local music store.  Way beyond my pay grade at the time.

My first Cakewalk product was Professional 6.  Before that, I'm embarrassed to say, but but my first PC sequencer ate my first real project, and I jumped to Cakewalk as a result!  Never looked back. I have tried other products too. 

Before that, it was an Alesis MMT-8 hardware sequencer, and a Boss DR-5 drum machine.

Over time I became very interested in the use of virtual instruments and real-time effects, as PC's became more powerful.  I upgraded to the Producer edition around Sonar3 (not X3) due to the included plugins. I think that Sonar Platinum offers a very broad feature package, out of the box.  There are plenty of tools that you can dig deep into, before exploring 3rd party plugins.  There seems to be an attitude that if something is free, or cheap, it must be worthless.  Not true.  There is mucho competition in this area.

Bottom line, is that there are many choices out there now.  If you are a pro, and make a living with this stuff, then it becomes a question of why not invest in the best tools?  If budget is not a consideration, then pick and choose the best tools for your trade.  If you know what that is.  Otherwise, Sonar Platinum offers an awesome cost-effective core baseline of capabilities for you to learn from, and then expand on from there ...

Also bear in mind there is a demo version available. For a period it went to 2 months in duration, but not sure if still active and does not allow saving the file. If you have old Pro Audio 9 projects, you can open them and play with features to see how they work.

In your situation the lifetime updates is a good deal, since a chunk of that resolves the "paying for bug fixes" complaint that had been occurring for years prior.