Even thought sorcs can sacrifice more gear, thus attain higher Mfind %s.... A hammerdin can mfind EVERYWHERE and faster than sorcs (except maybe a max dmg firesorc Vs. andariel due to his inbuilt negative fire resist)
Fishymancers to start out with, since they kill efficiently when untwinked.
Sorcs, those not dependant on fast cast items can kill fast with insane amounts of MF (and even getting to 105% FCR and 500% MF isn't hard when twinking).
Barbs can wear the most MF, but diminishing returns make it not worth it. Horking CAN make it worth it, and gold find = more gambling = more good rares.