Here's my takeaway from what i could see (hear) from videos, demos and this thread.
These are among the best solo strings on the market imho. I´m pretty sure that, with knowledge and good programming you can make both work well.
I've heard that SsS is more orchestral / cinematic oriented, to be used on top of Spitfire libraries, but i can´t deny that this tone is awesome for pop and intimate stuff too. Don't judge me! I just like it for everything from what i´ve heard.
On the other hand, i feel that Hein is a lot more flexible and tweakable (and has more instruments), but the "default" tone, at least from what i´ve heard, seems pretty classic-oriented to me, but the fact that its so flexible and made to work with anything, makes it not a problem at all. I like the attention to the smallest detail this library has and its vibrato page is awesome.
Both are Kontakt and NKS, which is a nice bonus for me (Komplete Kontrol 49 here).
The fact that i already have SCS, its cheaper (going even cheaper in a few days) then Hein and i liked the "default" tone more, makes me want to choose SsS.
And the fact that Hein seems more flexible, with more instrument options and its very dry to work well with any library and any project, makes me want to choose Hein.
At the end of the day, is kind of Brazil x Argentina (football / soccer - for some - analogy! Sorry, brazilian here, so...). Both are great teams with big stars and championships. There's simply not a definitive answer about who is better...
Due the opportunity, i´ll go with SsS for now. If it doesn't solve all my problems, i´ll pray for a Black Friday deal with Hein to get it too.
My big thanks to all of you for the tips and patience to read all this. lol