We could all talk about that until the cows come home...and we have, and the only conclusion is that it means something a little different to everyone. Just like people are individuals, so is every sub, every Dom, and every relationship.
If it's a relationship that you're after, don't worry so much about what kind of sub you are/aren't or whatever. Look for the person that makes you feel good to be with them. Just like regular dating, just with extra spice on the side.
Hell, if they want to call themselves a sub and still do the whipping, you might confuse everybody but if you're both happy, who cares?