djwolf
Secondly, there is mixed information here.  One suggestion is to download the new Bandlab as a separate installation.  Why?  I'll only ever use one of them.  The logic behind this is that the new platform will use "Most" of my effects.  Unfortunately, the effects that are listed as not supported by Bandlab in the comparison chart are the effects I use.

Cakewalk by Bandlab (CbB) installs itself alongside Sonar, in exactly the same way as like Sonar Platinum installed itself alongside Sonar X3.
 
The effects are listed as not supplied by BandLab. They are all 100% supported.
 

djwolf
Another issue is SSD space.  Two installations would require two copies of my instrument libraries which are many and huge - 1.2TB.  Two installations would require a significant financial outlay for new SSDs.

 
You are not required to install two copied of your instrument libraries. It will use your existing ones.
Both the CbB program folder & the CbB content folders are around 200MB each - so it will take up around 400MB of space.
 

djwolf
The next issue arises from a practice that has become pervasive across the internet - corporate connectivity for users.  Will I be able to install and use Bandlab if I don't own a mobile (cell) phone (and never will) or don't use anything with "cloud" in its title or operate my studio PC without an internet connection?   Without knowing these things, overwriting my current Sonar installation with Bandlab could be disastrous. 

 
You need an internet connection to download the BandLab assistant which is in turn used to download and authorise CbB, just like you did with Sonar Platinum with the Cakewalk Command Center. 
 
The BandLab assistant works in exactly the same way as the Cakewalk Command Center in this respect.
 
Once its installed / authorised, you don't need to be connected to the internet any more. You will of course need to be connected to download the monthly updates.
 

djwolf 
Thirdly, I don't care about the money.  It is a fact that without a financial transaction, there is no legal liability.  EVERY free software version is always a cut-down version of the one you must pay for.  What was I supposed to think when I read that this free version would support "most" of my effects?

 
Really? are there paid versions of Facebook, Internet Explorer, Firefox, Google Chrome, Libre Office, Open Office, Twitter, most Linux distributions, Arduor... I could go on....
 
The bottom line is, to avoid confusion just treat Cakewalk by BandLab in exactly the same way as you treated Sonar Platinum when you had Sonar X3. It's really just the next version of Sonar.

djwolf
There is a lot to respond to here.
 
Firstly, I have been using staff-lined notebooks for the last 45 years.  Now I have Sibelius which is fine for printing out the final instrument parts but I refuse to invest time I don't have into understanding another digital processing program...  So, Sibelius is just a score printer for me.
 
Secondly, there is mixed information here.  One suggestion is to download the new Bandlab as a separate installation.  Why?  I'll only ever use one of them.  The logic behind this is that the new platform will use "Most" of my effects.  Unfortunately, the effects that are listed as not supported by Bandlab in the comparison chart are the effects I use.
 
Another issue is SSD space.  Two installations would require two copies of my instrument libraries which are many and huge - 1.2TB.  Two installations would require a significant financial outlay for new SSDs.
 
The next issue arises from a practice that has become pervasive across the internet - corporate connectivity for users.  Will I be able to install and use Bandlab if I don't own a mobile (cell) phone (and never will) or don't use anything with "cloud" in its title or operate my studio PC without an internet connection?   Without knowing these things, overwriting my current Sonar installation with Bandlab could be disastrous. 
 
Thirdly, I don't care about the money.  It is a fact that without a financial transaction, there is no legal liability.  EVERY free software version is always a cut-down version of the one you must pay for.  What was I supposed to think when I read that this free version would support "most" of my effects?
 
To explain my "CPU power" comment more accurately: I was having issues with my 'Interrupt to process latency' creating an unstable audio environment.  To fix it, I removed all cloud and internet connectivity in the registry to a machine that is not connected to the internet.
 
Finally, let me apologize for my negativity.  I have good reasons but don't want to bore you with them.  Eventually, the lack of updates from Cakewalk will conflict with my driver and hardware updates and I will have to download Bandlab or migrate to another DAW.  I will make that decision when it is forced upon me.                

I don’t usually reply to such long posts, but your luddite attitude got me. To take your points :

SECONDLY : fwiw all my Splat pluggins work in CbB. Just because ots not listed “somewhere” does not mean it won’t work. Do some research.

ANOTHER ISSUE : if you know what you’re talking about, why install libraries 2x ? Just point the relevant software towards the said library.

NET ISSUE : no, you need to connect to Bandlab Assistant one time to log on to your Bandlab account then download the latest version of CbB. My PC is permanently connected to the interenet and as long as you do jot open dodgy mails or visit dodgy sites you have nonproblem.

THIRDLY : CbB is NOT a cut down version of Splat. Its also worth noting that CbB has been updated taking care of quite a few bugs that will never get fixed in any other versions. Again, don’t believe all you read, try it out. And yes, you should care about money.

CPU : do you have the relevant options checked so that sonar can use multiple cores and also core balancing for vst’s ?

NEGATIVITY : we don’t need bleedin hearts for sure, thats your problem, but c’mon, upgrade to CbB and save yourself any hassles - moving to another DAW will mean a very steep learning curve, so why not stick with Cakewalk, which i’m sure you know.

YMMV, so don’t take my comments too much to heart. Only you can help yourself.

BestJerry