Only my Orch Straings 1&2 have been upgraded to Extended. My additional upgrades must be done gradually for financial reasons... 8 of my 10 volumes remain in Standard (minus the Extended trial period...)
It's been a long time since I've used FE and didn't use it for very long, However, there are two things for me which make the Cube's Standard Edition stand out-- the interface and the quality of the sounds. Now, some people may be just fine with the FE/PE bit depth, but the interface is SO much easier to use and so much more flexible since it no longer ties me down to using Logic and EXS24 (in my case).
I do remember feeling a substantial difference when getting PE for the sheer quantity of available sounds. I really didn't accomplish much with FE because I badly needed the PE samples. More than articulations, the third chair wind instruments were sorely missed in FE.
At least with VI Standard you get a smattering of instruments across the spectrum, even if you don't get all available articulations right away. The interface alone takes the agony out of dealing with the FE/PE perf tools. Plus, it saves on having to load 10 instances of one insturment to access a variety of articulations, etc. Having all of one instrument on one track brings relief to the brain in all versions of VI.
But for me, the 24-bit depth has made a HUGE difference. The audio format is clever-- the way the files decompress and stream on the fly.
The thing one must weigh is cost versus features. That the VI Cube has an easier purchase structure than FE/PE did made it worth it for me to take the plunge. You bought FE (with no picc, Eng. hn, bs. clar., contrabsn, etc.) , then you bought the PT separately-- without which FE/PE were fairly useless. Then, you bought the PE upgrade and found yourself with boxes stacking a meter high or so. It was really awkward, imho. (But I did it!!)
With VI, everything is tidy. Upgrades are a matter of unlocking features already installed with an authorization code. No more huge boxes to buy, no more separate software for essential performance tools... etc., better sound, well integrated interface...