I don't think the parallelogram feature actually helps much in braking. I know it looks like it should, but once you try something else you've got to wonder what Shimano is thinking.

I had XTs and switched to Avid SD Ti in 2001. As I was installing them I marveled at their weight (less than half the weight of the XTs) but wondered if I had made a mistake. After a short break-in I realized they were at least as good as the XTs, weighed a lot less and seemed to be quieter.