I only buy tubes with unthreaded valves because the threaded ones wear out the rubber gasket in pumps. Michelins are unthreaded so I only bought them for years when Performance had them on sale. However, Performance never has Michelins on sale any more and the last batch I got seemed to have problems with the valves wearing out, so I've been buying Torelli tubes from my LBS. He sells unthreaded Torellis for $5 each, which is a bargain these days.

I've had bad luck with Performance tubes, so quit buying them. First, they are all threaded. Second, I seemed to get more flats with them.