I started with polysulfone, the ones with the springy-things in them to seal off when you disconnect so nothing spills out. At first I loved them, but soon found that the springy things just serve to clog up with hop (even when using a false bottom) during whirlpooling. Major PITA. Eventually I drilled out the springy things so it's a straight shot through, and this solved the clogging problem. But then the liquid will spill everywhere when you disconnect; to solve this I put a quarter-turn stopcock just upstream of the disconnect. It works great now. A little wonky with the stopcocks in there, but it works. There's probably a better solution for disconnecting and stopping flow so I'm hoping to see other responses here. But overall the polysulfone are just fine. Just keep some keg lube handy for the O-rings.