Need help in choosing Acer Laptops

I currently own an Acer Aspire 4736z, and I plan on selling it to buy another laptop simply because the 4736z can't handle gaming. My budget is around $600-ish, and I'm looking to buy an Acer 5742G. However, I found that there are several different types of 5742, and I am confused as to which one is the best one for me (budget-wise, and function-wise).

Here are the specs of the two 5742s:

Acer AS5742 i3 (for some reason, there are two types of this model in this online website I found. The difference is the RAM and the graphics card)
INTEL CORE I3-380M
2GB DDR3/4GB DDR3
500GB HD
GEFORCE GT540M/ATI Radeon 6370

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Acer 5742G GT540

AS5742G
i5 480
2GB DDR3 500GB
GeForce GT540 1GB


So, which laptop should I buy? Or are there any other laptops around the $600 area which are better? I will mainly be using the laptop for gaming purposes, such as Starcraft 2, COD, etc.

Thanks in advance!