The real benefit to a cease-fire (rather than peace treaty) is that either side can attack again at any time, resuming the hostilities. This means you aren't stuck with a ten-turn waiting period before you attack again.
EDIT: I haven't tested this part, so I can't vouch for it, but I've read that cease fires also help with overall diplomacy. Each time you declare war on a civ, you take a diplomacy hit with other civs for "You declared war on our friend." If you don't sign a peace treaty then when you attack again you aren't declaring war (the cease-fire is a temporary pause in the war) and therefore don't take another diplomacy hit with all their friends.