Well, now that my computer is playing with a full deck again, here are some observations, for which I seek confirmation contradiction, comments.
Studio is needed for notation programs, such as Sibelius, Finale. It is also usable with Sonar, in my case, Sonar 2.2. Disadvantage is that my cpu usage is quite high, seemingly regardless of number of instruments. It is necessary to load Studio before loading Sonar, my most common usage. Instruments can be altered at will once Sonar is running. Advantage is that if intend to review or edit a few pieces, and have the right templates saved and loaded, I can quickly switch between files. Recording as wav options are either the record to file of Studio, or the Sonar record options, which require some experimenting for levels and reverb.
VST and DXi seem to function about the same, except that it appears that VST is slightly less demanding on the cpu. Both are quite significantly lower than Studio. Recording a wav file is accomplished by "bounce to tracks" option, and is simple. But, both VST and DXi cut off sharply at the end of the last note, so to avoid that chop, it is useful to add a note a few bars later, which will be easy to remove after the recording is done. Big disadvantage is that the VST/DXi settings must be loaded for each file you wish to view or edit, which can be quite time consuming to switch from file to file, a real pill if you are demonstrating some works with a hope of your listener adding your works to his repertoire, or to get a "spousal test" of various versions of the same piece! Saving your file with settings intact causes the file to be agonizingly slow to load.
Aside: what I refer to as The Spousal Test is very useful not only for spouse (or Significant Other, according to current terminology), but good for using with anyone who enjoys music, has listened to a lot of music, but has little or no musical education. If you person says "Huh? you might get some useful information, especially things like, "hey, that doesn't seem to follow or fit the rest." Bear in mind that the majority of your listeners will not have much musical education.
But, both VST and DXi cut off sharply at the end of the last note, so to avoid that chop, it is useful to add a note a few bars later, which will be easy to remove after the recording is done.
To prevent this from the last not from getting cut off when bouncing go to the tracks and lengthen the end of them (kinda like trimming, but the opposite). The silence at the end of the will still be there when it's bounced to audio. Took me forever to figure out to do that.
You can also add a note, at the end of the file, that is completely out of the range of the instrument, low or high. The note will not be heard but it will prevent premature cutoff of the file.
It just struck me that you can add anything that the sequencer must respond to, for instance, what I did at the end of the Presto of the Moonlight Sonata, was to add a sustain pedal on the first beat of the bar after the ending. No sound, no mess to trim.