Melodyne is the same in both - the "Essential" version. A common upgrade (and one offered by Celemony upon your Sonar purchase) is the $150 to "Editor", which has a few significant feature advances (such as timing editing, vibrato editing, note transitions, etc).
 
Good point about the laptop. It's probably a good idea to invest in better hardware and get smaller software upgrades as you run into limits, considering it's relatively hard to upgrade laptop hardware.

IMO Producer is and always has been easily worth the extra. Melodyne is the same in both and either way requires the upgrade to Editor as Essential is pretty basic. AD blows SD away.

I agree but the question is if you really need all the extras it offers right away. I got like 30 BlueTubes plugs that I have hardly touched. I like BReverb but one could easily substitute Valhallaroom for 50 bucks. Many people prefer EZDrummer or another drum plug over Addictive Drums. Producer is good value but the individual parts that make it up are replaceable by choice alternatives, that can be bought when needed and won't be locked to Sonar (like the BTs are).

Flashart
Is Melodyne the same in both?
And would Studio give me enough to produce a small orchestra of instruments?
I feel I need to give you a bit more info, I'm also getting a laptop to run it. If I get Studio, I put more cash to the laptop and vice versa.

Is the laptop going to have an SSD drive? If not and it is a solid state drive then I would recommend planning to put some money aside for at least a 7200RPM drive that does NOT have the word "Green" or some such nonsense in the title. You want a good, stable, FAST C drive. Many laptops come preloaded with energy efficient drives and/or lower speed drives that will have serious impact on your work. Really if the CPU is above the recommended specs and the laptop has 8GB of RAM then that is more than enough to run Sonar reliably. The problems will come in with a slow drive that is designed to fall asleep despite your Windows power management settings.
 
So yeah... no need to go too crazy on the laptop as long as it has good, recommended hardware and you make sure you do a clean Windows install (to get rid of bloatware and wonky factory configuration stuff) and do a bit of tweaking to make sure it's not gonna have things like ports, drives or the entire system falling asleep.
 
You might just save yourself significant money that way which could be better spent on a good interface (which you already have so never mind)), external drives for storage and streaming samples, a good internal drive if the included one is insufficient for audio AND getting to enjoy the benefits of Producer.
 
You would probably be able to make a much more informed and cost effective decision about this if you start a thread asking about laptops in your price range that will run Sonar. You could save literally hundreds of dollars and end up with a better system than you would have otherwise. Cheers.
 
edit: You may however already be aware of all that already. If so my apologies but as a completely cheap bastard myself it pains me seeing people spending money unnecessarily.
 
I've priced laptops that would be very capable of handling Sonar after some TLC for $500-600 and others that could give my tower a run for its money for a couple hundred more. I could probably force my three year old $260 Acer to even run X3 in a limited capacity.

Beepster
I've priced laptops that would be very capable of handling Sonar after some TLC for $500-600 and others that could give my tower a run for its money for a couple hundred more. I could probably force my three year old $260 Acer to even run X3 in a limited capacity.

Laptops have tiny screens.  If that isn't bad enough, they're slow and very limited disc/ssd-wise.
 
Being able to run X3 is not the same thing as running it in a way that you can enjoy.
 
I use my 14" laptop when I'm away from home and it's really painful compared to my floortop and 30" monitor.
Still, it's way better than nothing !
 
 

I chose Studio over Producer because I saw nothing that was going to improve what I do with Sonar. We each work differently and we each will use certain tools to get the job done.
Studio is exactly the same in all regards as far as it's workings and features go. As said, Producer gives you a good pile of extra efxs and soft synths and if you want these then it's worth the extra  $150?? (depending on the deal of the week) . It's a no brainier. Look at the list. Decide if you really need them. You can always upgrade later anyhow. 
Myself I'm more than happy with what I have and don't use 1/4 of that. I have still haven't had to activate Melodyne. I prefer to sing in key. 
 
And I will add that unless your planning on doing remote recording, don't buy a laptop for a DAW. Laptops are obsolete and not a very good value for your money. 

I suppose some might argue that towers are obsolete, but I finally moved X3 Studio from my laptop(it was all I had for a while) to a newer 64 bit tower. It is soooo much better. The laptop HD was too slow, a not uncommon issue.
 
Flash, either way, you will like the flexibility and control you have in X3. It will take some getting used to, so be prepared for that and read the help files. I did not like the SHS7 interface at all. It was intended to make things easier for the novice, which I guess it did, but it was ever so cumbersome if you wanted to stretch your boundaries.
For me, X3 Studio is more than enough, but I already owned the full versions of Rapture and DimPro, as well as numerous third party plug-ins.
As noted, the core X3 program is the same in all three versions. The difference is in the extras.

There's actually a few parts of Plain X3 missing that are sort of critical to me.  
Audio Snap for one. 
No Pro Channel
No SPMTE / MTC support. 
No Surround mixing ( not for me but lots of people use this. ) 
Then the instruments your missing some very useful synths, a long list. 
And then a whole lot of Efxs are excluded. Most important to me was LE 64's
Studio has most of the best stuff so was way more bang for the buck than plain X3. 
I see scook already posted this link but it's required reading if your going to compare versions. 
http://www.cakewalk.com/Products/SONAR/Versions
 
 

I can only speak personally.  Producer is definitely worth the extra to me, as I have felt far less need to invest in third party products since upgrading.
 
Apart from all the instruments, I would miss the two PC compressors that come with Producer - the PC76 and the PC4K Bus.  I use them all the time.
 
IMO Addictive Drums is far better for most needs than Session Drummer, even though I don't use it much - I already had Toontrack stuff.  If I hadn't already got the Toontrack stuff, I would probably have been happy with addictive Drums, and stuck with it.
 
So, I think the extra for Producer is a great deal, but only if your hardware is up to it, as others have mentioned.
 
Spending money on upgrading an underpowered computer is the only reason I would see to buy the Studio version.  Even then, I would try to save a bit more cash and upgrade my computer AND get X3 Producer, if at all possible.
 
Let us know what you decide, and come back with any questions.  I upgraded to X1 from Sonar 6, and would have been lost (and bald) without the help of this forum, and Scott's "Sonar Power" books.  Another great book is "The Power in Cakewalk Sonar" by William Edstrom (It is about X2, but still covers most of the workflow in X3, and comes with a DVD).
 
Good luck.