GTX 680M SLI

Hello guys! I can't make a clear decision. I'm about to buy a laptop and currently looking at Lenovo Y50-70 with GTX 960M; i7-4720HQ; 8GB RAM; 256GB SSD. But also I found used Alienware M18X R2 laptop with 680M SLI; i7-3840QM; 16GB RAM; 1TB HDD on similar price. I'm casual gamer and would...