I do not agree that the Synchron Series is a step forward. It's just different.
From my perspective, VI-series is what makes VSL unique, still to this day. Ever since the very beginning there have always been libraries that were recorded in some remarkable scoring stages and then marketed as "The Ultimate Film Scoring Library!". For many, many years VSL never fell into that trap and instead proved the VI-series to be the most detailed, versatile and flexible virtual instrument out there. It was not only for those with only film score in mind but also for everyone interested in orchestral music of different genres (not least, classical music).
I own them both and have different use cases for them, sometimes I mix them with great results.
However, if I had to pick I would always go with VI-series. I could replace the Synchron Series with other vendor products, but I could never replace the VI-superheros - there is just nothing like it.
Definitely! I evolved a system using VI based first upon having underpowered computers (back in around 2005), which, if I was careful, I could tweak to use VI at full power, just with more intermediate steps. Now that computers are so much more powerful and cheaper, that is no longer an issue but all the simplified setups I made - which were simplified only in technical requirements, not musical which were huge - are still valid.
Many people first coming to VI or Synchron think that you have to have a Hans Zimmer 5 Billion dollar studio or whatever he has to use the samples properly. But actually, you can use VI with the simplest set of selected articulations on a single humble computer and play something just as well as Zimmer ever did. It is because of the methodical sampling style of VSL and extreme purity of recording which is uniform across all the VI instruments, and allows you to create templates very easily that transcribe across radically different instruments. This versatility I have found in no other sample library though I've used a lot of them over the years. It is the kind of versatility that the SYMPHONY ORCHESTRA has. It is a sound bank that has yet to be matched by anything else..