I've got a stock caliper in the garage, I'll measure it tonight, but SC Drew already did the measurements and came to the conclusion that the f-body calipers actually have less piston area than the stock calipers. Distribution is just that much better.
As for why people complain, I really think it's a bleeding issue. With the angle we have to mount the caliper at, the bleeder isn't really at the highest point anymore, so there's always some trapped air in there. I'm planning on bleeding mine while they're not bolted to the knuckle next time to see if it makes a difference.