Having 4GB+ RAM isn't the only reason to go with a 64-bit o/s. Multicore processors will be utilized to their full potential since they are 64-bit and certain data encryption routines can be handled better. At a hardware level it would be better to go 64-bit as long as their are drivers to support it.
As for games/apps there can be some improvement in performance in relation to hardware but generally the software needs to be specifically written for 64-bit.
Imo, go with 64-bit to be future proof.
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