Apart from on a Cr which has a really loose std piston you probably wont notice much difference between any other pistons in terms of performance, saying that the one area to look as is as MXPIMP pointed out-some pistons come without windows/lightening holes, this generally is done for more bottom end but may sacrifice top end to get it.If you are after a trade in bottom for top then look into one of these type pistons from wiseco/vertex, if not get the std type piston from vertex or wiseco-both are very good and should last better than the OEM set up.