Biggest difference in sound to my ears is the legato transitions.
I have both (CSS and CS2) and seems like I am one of the few who finds the general sound of CS2 a tad better than CSS, especially for this piece by Samuel Barber.
The statement given above that both are meant to be totally different is a bit over the top. Actually they are not. I have variuos string libs (VSL Orchestral & Appassionata, Adagio,Sable, Soaring Strings, Light and Sound, CS2, CSS) and CSS is by far the one sounding the closest to CS2. Was also a reason for me to buy, because I still adore the sound of CS2. With little tweak you can make both sound identically.
CSS and SCS sound quite different, it is like apples and bananas. So which sound do you prefer.
I would not argue over the amount of articulations. The articulation list in CSS is more than reasonable. SCS will give you a lot of articulations you will most probably never use. Most people fell in love with the flautando of Sable and it is used everywhere. So in the end, you will pick those you like, flautando probably being one of it, and use this selected collection all the time.
That does not mean you should not go for SCS. But don't let the long articulation list be the reason for it.
This long articulation list remembers me of old VSL times with endless tweaking and patch choices. Multi-patches are more favoured today.