Ok, firstly
> Gaming laptop
Enjoy you're 80% markup.
Remember that in the 15-11" range Apple make quite competitive laptops, with so many games now supporting Mac it is a viable option. You can of course install W7 on the laptop afterwards.
I think an M1#x will be expensive compared to a Mac, but a good choice none the less.
Comparing the $1500 M11x to the $1500 13" Macbook Pro will show you that the Macbook holds its own perfectly well, and infact is superior in some ways.
Indeed Pyro, but the M15x is way more expensive, well over $2000, which is far out of his price range. The only valid Alienware laptop is the M11x, where as Apple has several laptops in the price range, but I don't think they sell any 11". So you understand that you cannot compare 2 identical sized laptops from Alienware and Apple whilst remaining within his price range (as best as possible).
I consider 11 and 13" to be quite comparable, and both are a lot less draining on the wallet.
A bigger laptop does in some ways imply cheaper prices, but between 11 and 13 the price disparity should be negligible.
Besides that, OP did not specify a size, so both are valid choices.