Okay so i basically killed my old laptop and now I am starting medical school, so i need a new one.

I have basically narrowed it down to two companies: either Alienware or Asus

I would like to have a sleek, powerful, long battery life computer but also realize that by getting an alienware for performance that i will be giving that up. I am okay with that because as history has taught me, if I get something top of the line now that is very powerful.. it will still be very good in a few years.

I have looked seriously at the Alienware m14x and like that one a lot as it is considered portable, and also the G51 for the asus computer. What should i do for the best performance? If anyone has these two computers let me know how you like them. Discuss!

Get a mac, they have like a 10 hour batter life

Eww, no stay away from Dells. If you want a stable laptop for school get yourself a Thinkpad. great brand and reliable! 

acer laptops have a spot next to the touchpad that emulates the middle mouse wheel, makes browsing txt, pdf or the interwebs a lot easier

also, im not sure where you live, but in na sony usually has a deal that takes 150-250$ off the price of their vaio laptops if you can verify that youre a student, might want to look into that

Pretty much this.

Is money a non-factor?

Just curious why you'd want to get the Asus G51? Isn't that an older version now?

If I wanted to get a 15" Asus laptop (good for gaming) then I would go for a G53 one like this:

http://www.btotech.com/product.asp?pf_id=asus_g53sw-a1

It has one of the newer Intel i7 Sandy Bridge cpu's and a 1.5gb GTX 460m gpu.

I was actually considering getting one of them (when they still had the older i7 cpu's).

Instead, I got a very portable w/long battery life MacBook Air. I'm loving it in the 3 months or so that I've had it. It's very easy for me to take it around as well being very thin/light. I do most of gaming at home, so I just built myself a really nice/powerful desktop ( http://gamrconnect.vgchartz.com/post.php?id=4012535 ) ;-p

get a sager istead of alienware

Do you need that performance on the go?  If not I'd go for a relatively cheap laptop and build a desktop.

This.

If you get a laptop with a gaming GPU at all, battery life will be abysmal.