Never assume, cause it makes you look like a retard-in
Some prot pallys dont even judge.
Prot pallys need all the mana they can get, so they will be judging wis 90% of the time (if they are even judging)
Ret has a talent that "replenishes" their mana, while a prot does not. See
http://www.wowhead.com/?spell=31876 in the 7th tier of the ret tree allowing them to judge light and still get the replenishment effect.
No one gives a shit if you're alive and cant do any damage
Again, both are of eaqual importance, one does not outweigh another. Prot = Wis, Ret = Light.
Or better yet, make a shift macro and judge both.