Can someone please tell me the differences between these Graphics Cards?

Hello there! Sorry if this is the wrong section of the forum to post this thread. Recently, Aliennware has released its new refreshed 2013 models which I think look wonderful. However, during this time I was also planning on purchasing the 2012 models. Now, originally I was going to get the m14x with a 2 GB GDDR5 NVIDIA® GeForce® GT 650M with Optimus™.p However, since the refresh, this option was removed so all that remains is a 1 GB GDDR5 NVIDIA® GeForce® GT 650M with Optimus™. Now another thing which I’m not a fan of (but I totally understand) is the price increase but it also has upgraded graphics cards from the 700 series! Now there are 2 available for the system (still a m14x) but I’m currently looking at the NVIDIA® GeForce® GT 750M with 1GB GDDR5. SO please tell me,what are the differences between the
NVIDIA® GeForce® GT 750M with 1GB GDDR5 and 2 GB GDDR5 NVIDIA® GeForce® GT 650M with Optimus™? Which provides the better performance?

Thank you for your time!