flaviowolff :
As I'm not sure if the 1080p screen is actually better (contrast, brightness, etc) and I favor performance, I will stick with the 768p.
If you aren't sure, then you need to err on the side that it is. In the vast majority of cases, a 15.6" 1920x1080 display will be of substantially better quality than a 15.6" 1366x768 display. And any exceptions to this I could probably point out (such as with a couple of the older ASUS laptops that used the AUO B156HW01 V5 junk 1080p display). And as far as currently-selling laptops go, out of the ones I have seen, I have not seen a single exception to this. If you get a 15.6" 1366x768 display, the quality/contrast is going to be pretty bad. If you get a 15.6" 1920x1080 display, the quality/contrast is going to be great.
Plus, that aside, a lot of games are going to run just fine with a GT 650M on 1920x1080 anyway. Most will, and under decent settings at that. You're greatly
underestimating the performance of the GT 650M. And having that faster GPU is going to open up more options to you, both in terms of currently-available games and in terms of future games. If a game is too intensive to be run on the GT 650M @1920x1080, you will still have the option to start running at lower resolutions. With the slower GT 640M @1366x768, you're worse off.
Buying a laptop with a slower GPU and a lower resolution + poor quality display, instead of a laptop with a faster GPU and a higher resolution + decent quality display, is a terrible idea in the vast majority of cases. There may be some cases that might make it better, such as an eyesight-related need for large text that cannot be accounted for by OS DPI scaling, but gaming isn't one of them.