I find it hard to justify $1600 for a stock clutch with a different flyhweel so that put the LS9 variety out for me.
I too was torn between the McCleod and the Mantic line and ultimately went with the Mantic double after talking with Chris and Doug@ECS a few different times over the course of a month. Considering ECS does A LOT of drag racing and they use this clutch almost exclusively in their builds, I feel good about putting it in my relatively tame 500whp(150 shot in the future) build.
They swear it will slip like stock and hold up the dragstrip abuse so I'm very excited to get it installed and have my own impressions.
I did a thread about the 3 clutches you mentioned about a month ago and got some interesting information from others experiences.
Good luck and keep us posted with what you decide.
P.S. my Mantic is scheduled to arrive today so I'm anxious to see it in person as I hear the craftsmanship is second to none