fuck is used to describe a LOT of things... errors "oh fuck", people "that fuck", actions "let's fuck", or as a word to increase aggression "lets beat the fuck out of him"... and im sure there are many many more examples..
cunt... well... it just sounds dirty... not a good dirty.. a bad dirty... and call the wrong woman a cunt and you'll be waking up looking like a cat just line danced on your face.... not good at all...
i think cunt is like a trump card... for us guys... bitch and whore and slut have lost their "shock value" in fights anymore.... but cunt... thats like a low blow when the refs not lookin...