Not sure what you mean by "4400" on the 14" spec, however if I'm reading right, it's a built-in graphics card while the 17" has a dedicated card in which case it's a no brainer: go for the 17".
There are many factors, but the most important single element of a gaming laptop is the video card. Ideally, you should compare the graphics cards on one the many GPU comparison sites to see which gets the highest rating. Some of the better sites even let you compare game-by-game.
Obviously, the processor matters too, but even the faster processor is going nowhere if the graphics card ain't cutting it.