Power cleans obviously grow big bodies which is evident in college and pro football. Those guys put on mass faster than anyone I've ever seen.
I've seen maybe 3 people in my life doing power cleans and none of them were MMA. Most of those guys stick to machine movements, Bench press and bicep curls.
I think the biggest problem with the C/J, Snatch, etc.... is that people, personal trainers, mainstream magazines, try to recast these exercises as general purpose exercises, and they don't truely understand them.
The Power Clean, C/J, etc..... are exercises that need to be trained with relatively heavy weight, in low rep ranges, to have the most effect.