M17x R3 vs M14x R2

Hi guys. Im planning to get a used alienware, but im confused as to which one is better for gaming.

I narrowed it down to these 2:

M17 R3 ($1,200.00 no more warranty)
i7 - 2820qm
12gb 1333mhz ram
320gb HDD
ATI 6970m graphic card
Intel(R) Centrino(R) Ultimate-N 6300
Blue ray reader drive.
1920x1080 screen resolution.

M14 R2 ($1,500 with 6months warranty)
i7-3720QM
WLED HD+ (900p) display (1600X900)
Slot Load 8X DVD+/-RW Drive with DVD+R double layer write capability
- 2 GB GDDR5 NVIDIA(R) GeForce(R)GT 650M using NVIDIA Optimus(TM) technology
- Killer(TM) Wireless-N 1202 a/g/n 2x2 MIMO for Gaming & Video and Bluetooth(MY)
- Crucial M4 256GB SSD

Thanks in advance....