Assistance with finding ok laptop.

Hey guys so, this is a little sad, I went to school for a year for computers but it was more on how to build fix and repair and networking stuff, I didn't spend to much time geeking over which graphics card is better. So basically I'm having a little problem, I'm going to buy a new laptop (yeah I know they aren't as good nor cheap as desktops, but spare me I have no choice) and I'm basically down to two choices. I only have a 450 budget (shitty) but I know I can at least get a semi-decent computer for this much. Anyways if someone can tell me one thing the Radeon HD 7640G isn't as good as the Radeon HD 8750M right? I'd assume because of the numbers but honestly have no idea and websites give me different answers. Also the 8750M comes with 8 gigs of ram where the 7640G comes with 4. Anyways to look at specs I'll post links below.

Radeon HD 8750M: http://www.newegg.com/Product/Product.aspx?Item=9SIA29P1X89365 Radeon HD 7640G: http://www.newegg.com/Product/Product.aspx?Item=1TS-000D-001F7

P.S I know graphics cards don't make a computer but they have rather identical processors sooo. .. .