You get an experience bonus if you get through areas undetected and take people out non-lethally. It adds up since it is like an extra 200 exp bonus for tranq-ing someone rather than shoving your elbow blade through their neck.
You also don't burn through your resources as fast. This is a problem if you're not a experienced player and can't map where you need what and where everything is.
Is that even a question? PS4.
I'm not getting it at Christmas though, I'll be getting it sometime later just to keep an eye on any hardware faults there may be. I'll be getting a decent laptop before then.