HD 6570 vs HD 7750

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

or

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

I'm wondering which card is the best value card and if there is much of a difference between the performances of these cards with current modern games at 1920x1080.

Specs:

Low Profile
Pentium(R) Dual-Core CPU E5300 @ 2.60GHz (2 CPUs), ~2.6GHz
4096MB RAM
HD 4350 512mb
240w PSU

(pretty bad computer, but planning on building a new one whenever)