Cuddling has a more relaxed type of atmosphere where kissing it all depends. Kissing is either aimless and wonderful or it has an alterior motif (sex). Most people can't enjoy kissing when they're on guard wondering about what the next step is, usually with someone's tongue down their throat. If you find the right kisser, both cuddling and kissing fall into the same categorey of comfort.
"So tonight, when you're wondering what to say, or how you look, or whether or not she likes you, just remember, she is already out with you. That means she said yes when she could have said no. That means she made a plan when she could have just blown you off. So that means it is no longer your job to try to make her like you. It is your job not to mess it up."
-Hitch