I have the Dixis Pulley and I am very happy with it. I must say when people were talkiing about huge performance gains I didnt believe it. It truly is a night and day difference. My car is a bigger and badder beast since the pulley.lovelove
I have the EvoSport pulley and am very happy with it. However, if I were buying it today, I would go with RPI simply b/c they are a great shop with amazing customer service. The pulleys themselves are probably pretty comparable.
A "quick story" about RPI: I ordered 3 of the trunk badges from them - you know the ones about storing 3 dead hookers, 4 crying babaies, etc. Eloy actually calls me himself to tell me they are out of one on the ones I chose and spends half an hour on the phone with me discussing the M5 and various mods. I told him to send me any one he wanted as the third. Yesterday the mail comes and the badges are there. Eloy sent me 5 (for the price of 3), just to make up for the fact that they were out of one.