Are all bases created equal?

Hey guys, got a quick question, dont know if the answer will be quick or not though. My question is, when you get a set of bases, and you go to tweak them... can all bases be tweaked equally? Or at least to a certain degree of others? or are some bases a lost cause and will never perform that well?

wasn't sure if tweaking was all about the tweaker, or if individual bases had to be of good quality too.