Full disclosure --- we've never had a Murray Grey be a part of any of our beef tastings, so I can't really answer your question ... so, I'll just give you what I've got.
First, to let you know what we do, we prepare identical cuts of beef in an identical fashion and then sample each one and rank them -- nobody knows what is what until it's all over -- everything is considered from smell, flavor, juiciness, number of bites required to finish, etc. While we've had lots of these blind beef tastings, the beeves have varied at each one. We've not had each breed in each test, however, when we have had them side-by-side, here's how they compared against one another.
Dairy -- Jersey > Guernsey > Holstein
Dual Purpose -- Aubrac > Pinzgauer > Shorthorn (beef type, not dairy)
Dairy/BeefX -- Aubrac/Jersey > Black Angus/Holstein