Maybe I'm misunderstanding, but I guess you are not speaking about Synchron libraries, but Synchronized. But I may just understanding the wrong way.
I'm using a mix of everything. In some cases I prefer to go Synchronized, because it makes sense. For example, if using Dimension Strings mostly as a compact ensemble, SYzd is much easier. Special Keyboards and Plucked Instruments have better labelling when SYzd.
When needing Dimension Strings in more complex setups I prefer the old VI version, because I don't have to deactivate all the added impulses and effects before using them. There shouldn't be any difference in the available articulations. The same with Dimension Brass, that I only have in the VI version.
At the moment, my VI collections are easier for me, because I've create all the presets by following the same schema. So, I have a unique map for everything. If I want to layer strings from different libraries, the same map will drive them all from a single MIDI channel.
Several instruments are still only available as VI instruments, so there is no choice. Woodwinds, for example, or the more exoteric brass. Or some advanced articulations, like the ones in the Vienna Horn.
I'm still not in love with the Synchron world, but I've been forced by the BBO series into it. I wouldn't probably have got Synchron Strings Pro without needing a match for BBO. It's a fantastic library, but not the best choice, as far as I can understand up to now, for what I do mostly. Yet, I know that we are in a courtship affair…
BBO contains some incredible instruments. At the same time, FX Strings 1 is probably one of the most precious tools I have. I'm therefore switching my VI collections to the Synchron Wide MIR room, so that I can match them to the new collections. They integrate really well. And the Synchron hall can be really impressive, even if not the sound I would have chosen before the others.
So, I'm in a hybrid setup, with a core made of VI, extensions from the Synchron/BBO series, and some Synchronized instruments. All blended inside MIR.
Paolo