Every time I try a different clutch I end back up with the Werks 4 shoe. I used the Mugen clutches and they feel really good but life was short and they eat into the bell. I also tried the Buku with no luck. I got a lot of slipping and heat from it. I also used the M2C 4 shoe for a while but it was a little soft hitting, even with all the tuning options it has.
I've had tremendous luck with Werks. I can get 4 - 5 gallons on a set of shoes and they don't produce near as much heat. My Mugen bells stay the same color their whole life. Clutch bearings last longer too.