i know two people that have the 15" MBP and both are satisfied with it. idk anyone with an alienware laptop but then again, they are overpriced for what you get.
i also know a few people with regular macbooks. they like them and i think they're alright, i just really hate their keyboard. God knows how much food is inside my laptop cause i eat a lot while using the laptop, so the macbook's keyboard is good for that reason. i just personally find it childish (the blackbook is better in appearance imo).
i haven't seen an asus laptop before but i have never heard anything bad about them. i would definitely go with one of them, especially if you plan on occasionally gaming.
this is what i think you should do:
if you want sub-$1000, go with the HP dv2000t. solid build quality, very nice appearance, weighs 5.25lbs, and has good options you can add.
$1200-1500: go to newegg.com and get a 14.1" Asus (A8J?) with a C2D T7200 o\and either the MRX1700 or 7700Go GPU. get a Dell D620 or macbook only if you won't game (has no dedicated graphics option). the D620 has a business graphics card option, however.
if you're going to be spending more, the MBP is a good option. i know there are other options out there but my brain is kind of tired and i had no need to recommend an expensive laptop lately so they're not quite at the top of my head. i really think the Asus would be the best option for you right now. it was $1300 last time i checked with a T7200 cpu, MR X1700 gpu, 1gb ram, 120gb hdd, dvd-rw, etc.
if you take any advice from my post, notice i only recommended 13.3-14.1" notebooks, except for the MBP. size does matter for college students, and 13.3-14.1" seems to be the sweet spot.