I really need to hear how (all by itself) 'controllable' the non to vibrato sound is. For me the GREAT weakness of ANY sample string section is its inability to do this convincingly without artifacts/phasing. For me if Sample strings sit for more than a brief moment without some change to vibrato (not just xfade between sampled layers BUT vibrato and I am personlly taken out of it.)
I would understand your Point, if you were talking about Solostrings, since one Violin alone do not produce any phasing while changing the intensity of vibrato. But: Synchronstrings I are Section-Strings. It appears to me not only quite natural if you have phasing effects between multiple stringplayers playing the same note especially while they are increasing their Vibrato intensity, I even think that is exactly what we want and expect to hear to make a difference between Soloist and Section. (While - If I understood right and can believe Embertone - It seems to be even possible nowadays to map Soloviolinsamples in a way that would allow xfade without producingadditional phasing problems.) However for Section Strings increased Phasing effects with increased vibrato seem to me not the problem but something quite natural.
