First of all, let me tell you that I think your string writing is beautiful and THANKS for the comparison!
Your post is just in time. I've done a lot of composing with VSL and it's only when I have strings-only parts that I'm dissatisfied with the results. I use a lot of modwheel, probably the equivalent of what you do with the breath-controller, and also a mix of legato and non-legato patches from the VI special editions - most of the time doubling those two.
The problem is that no matter what I do, the string section doesn't come across full-bodied and homogenous. I think the sound that you have in your dimension strings demo is closest to what I'd want it to sound like. As to the synchron strings, I haven't heard anything yet that - for my taste - provides the natural flow and vibe which I think is essential to strings.
In the end I'm kind of frustrated by the amount of time I have to invest into the string parts to make them sound acceptable. I've considered turning to different sample libraries, but I'm still hesitating because VSL samples have always been more than sublime. My feeling, however, is that I'm going to stray very soon.