duke132 :
So is it worth the upgrade ? and the money ? my Mac is in great shape and is lighter and thinner, but the performance on the dell is worth the change ?
Depends what you want to do with it. As you say, the Mac is thinner and lighter (the only Alienware laptop I've ever handled was so heavy it should have come with wheels and was actually too "thick" for me to type comfortably without a wrist-rest) and MacBooks usually have pretty good screens too. (Personally, I'm not a fan of Apple products, but credit where it's due!)
If you are happy with the MacBook's performance then there's no need to change. If you hanker after faster graphics and a beefier CPU and don't mind the weight and bulk, it might be worth the trade. Personally, if I'd been offered a similar swap back when I used a laptop as my main computer (many years ago) I would probably have decided to keep my small, light, bomb-proof ThinkPad X40 and simply build a gaming desktop as I really didn't need to game on the move. (And I can play UT Classic on the X40, anyway, which is good enough to while away an hour or two on the train.)
Only you can really decide, though.