As far as I know, Crucial RAM often matches or exceeds the quality of Corsair or Mushkin.. and vice-versa. The performance of RAM is always going to vary, based on the configuration it's used in (and what the user attempts to make it do). One motherboard (or chipset) may love the Mushkin, the next may prefer Crucial. It would be handy to look at all these manufacturers of very high-quality RAM and declare one of them as "THE BEST"..but that's not likely to happen.
Look at any of the testing/benchmarking sites.. most of them mention these 3 brands of RAM, most declare their preference.. and most of them prefer one or the other. Honestly, I haven't really seen Corsair at the top of anyone's charts lately.
Personally, I've used all 3 brands, and never had a problem. I tend to have better luck with Crucial RAM in an overclocking scenario. They certainly rank among the top few memory manufacturers at most hardware sites I visit. Including this one..
-JB