I used to have some of the lower end Shimanos MTB pedals - maybe 15 years ago? With the right (i.e. wrong) kind of dirt / crud, they became almost impossible to get out of. I tried the higher end Shimano, worked OK but the price was crazy.

I think Crank Bros was fairly new and I tried them -- no difference clean or muddy but I wasn't too keen on them initially, I think it may have been a bad match with the shoe. I went back to them a year or two later for some reason, loved them, and haven't ridden much else since.

The Crank Bros cleats are pretty soft brass, do wear out relatively fast, but I think that makes them easier to get out of.