Well, the 720 is better for some existant games and soon-to-be-raleased games. The 400mhz speed difference could be easily overcome by upping the 720's multiplier a bit; and I don't expect it to need mcuh extra voltage or cooling to get it to 3/3.1/3.2 GHz (but this is just my guess).
I know nothing about RAM
As was said, overclocking is easy, adding extra (stable) cores is not.
That third core can defiantly help when gaming, if only to handle all the background processes.
------------------------------If the automobile had followed the same development cycle as the computer, a Rolls-Royce today would cost $100, get a million miles to the gallon, and explode once a year, killing everyone inside.
PSA
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