Both are great first snakes. However, I would tend to lean more towards a corn snake. They are much more forgiving in just about everything; eating, temps, etc. That being said, as was already stated, a well cared for bp will do just fine, too.

One thing to possibly think about, is that corn morphs are a lot less expensive than ball morphs. You can get some very colorful and cool patterned snakes for not that much money.