When it comes to PIDs the auberins PID are actually cheap compared to most. You can pay a lot of coin for PIDs in teh commercial world.
I can't speak for the other PIDs, but I do know auberins stands behind their product, is there to trouble shoot, goes above and beyond what they are required to when it comes to warranty or product issues. For all those reasons I believe it is well worth the extra $15 each PID for the auberins product.
I have had my electric system rolling for over a year and a half and though I upgrade my panel, I still have my first original PID and it is working well.