Hello Mike,I have just about every major string library out there, and in terms of playability, Afflatus is an absolute breeze. It's much more user friendly than anything Spitfire has ever done, imo.
Afflatus also has ensemble patches that are true polyphonic legato, which allows you to play with both hands and achieve smooth legato transitions!
Tone is subjective, but in terms of realism? More often than not, that has more to do with the composer's programming skills.
In the right hands, a 20 year old string library can sound amazing!
With that being said, if you're set on Spitfire, then i highly recommend SCS. It's a great string library and can achieve just about anything you throw at it. It also has ensemble patches, and the flautando articulations are absolutely gorgeous.
Many people will recommend CSS, but i personally am not a fan of the playability, as I find it to be very cumbersome. Also, if you go that route, make sure you like the tone, because it has a dark, and sometimes even a "lo fi" sheen to it. The ensemble patch also sounds very synthy to me. Regardless, CSS is fully capable of producing some very beautiful results.
Good luck with your search!
I appreciate you sharing your opinions based on vast experience with string libraries. Tone is subjective indeed but from so many different demonstration and walk through videos that I have been watching, I have found that I keep coming back to Spitfire Chamber Strings. I just love the sound of it. It sounds warm and inviting and so rich and warm, like it just reaches out and hugs you, if you know what I mean?
The sounds from the Cinematic Studio Strings library do sound like they are specific to blockbuster cinema composition. I think they would work well for any movie with Dunce "The Rock" Johnson as the star, or any of the Marvel movies. Not so much my cup of tea but I can hear why many people love it.