a poly bushin will bind more sooner than the spherical bearing type will, but on most street cars this shouldn't be a problem as much as with a drag or road race car as a "typical" street car won't be put through it's paces like the others would, however if you're building a more canyon carver type car that will be pushed to the edge a lot more than a "typical" street car then you'd be better suited to use the spherical bearing type system. the sperical bearing one will probably be a little harsher and require more maintenance than the poly bushing type will. with the poly bushing one i'd imagine you'd just need to grease the bushings occassionally and that's about it as far as maintenance goes. the spherical bearing type would probably require more regular greasing and also probably require an occassional tear down of the joint to clean, inspect, lube and adjust the preload on it. that's my take on it anyway.