Basically, you are comparing a high clocked dual core with less ram to a lower clocked quad with more ram. Let's break it down:
1. More ram is better but 4GB is more than enough for gaming, especially if you can only afford a 5450 laptop version.
2. The quad vs dual will depend completely on the games you play. Likely there will be no difference though but:
FSX, dragon age, GTA4, and a couple other games would definitely need the quad core.
Other games would more likely take better advantage of the dual core however that said, the speed of each core on the quad would likely be enough to handle any game that can only use 2 cores anyway.
So I say the i7 system will be better for gaming.