I have both and they are great. My new girlfriend, who is not a snake person, actually touched the corn snake and thought it was pretty cool. She is interested in handling it, but not the others (ball, bull, rtb.) When anyone walks into the room, the corn snake will come out of it's hide and watch the person...if you go up to the tank, it will climb and see what's what (probably thinks it's getting fed.) The corn is very handlable, but is always on the move.
The ball definitely has more substance and moves slow...it will just hang out. The ball's head is very distinct from it's body...it looks like it has more expression...sounds weird, but just how it feels to me.
I'm in canada, so the corn is a lot hardier, as far as not needing as complex a husbandry and eats less, but eats regularly...balls are picky.
For a first snake, I'd say get the corn...smaller, easier to maintain, friendly and not as intimidating to nonsnake people. You'll have it and enjoy it for a little while before you go out and grab a ball for your collection...and you won't regret doing that in the least. Good luck