Unless your going to be doing serious number crunching, go for the (I can't believe I am about to say this...) Dell.
More memory, better GPU.
Not necessarily, AMD really is messing with people's heads this generation. 87xx series is actually very similar in performance to the 7730m (8730m=7730m). http://www.notebookcheck.net/Computer-Games-on-Laptop-Graphic-Cards.13849.0.html
(you are going from 512 shaders at a low speed in the 7730m to 384 shaders at a higher speed in the 8730m--both use 128 bit GDDR3 at similar speeds).
the two are about equal though a 640m beats them on average by about 20-40%. http://www.newegg.com/Product/Product.aspx?Item=N82E16834152377
Has a 645m (a little better than a 640m) and an i7.