Pardon my ignorance, but what are they? As I understand - a bushing is a piece of rubber/poly, how can it be "performance" or not? Their only goal is to provide that two mutually moving metal parts do not have a direct contact
The stiffer the bushing the less "give" they have and there for will stiffen up the ride. It helps those that like Road and Track events, on a daily basis, it wouldnt that much. For example, sway bar bushings are about 1/2" to 1" thick and plain rubber so...when you stress your sway bar the rubber gives and takes away from what the sway bar is supposed to be doing (stiffening your ride around corners). If you have a harder piece of plastic or polymer then it will increase the effect of the sway bar.