Definitely Del. He's a super nice and fun-loving guy while Neal was an uptight jerk.
You've seen Guy Standeven in something because the man was in everything.

I'd probably prefer Neil, with the mitigating factor that his yuppie stuffiness would keep him from ever becoming a close friend. Del, on the other hand, would probably ruin your life after a few days of being your friend.

I would prefer Neal as a business associate but Del as a friend

Neal is grouchy and full of himself. Del is goofy and friendly.
Most of Del's annoying qualities were his personal behaviors and things that you wouldnt usually see. How often do you usually share a bed with friends?

I'd probably prefer to be friends with Del. One of my best friends was a guy who I initially thought was an eccentric, unkempt weirdo, but after spending a significant amount of time with him, I found him to be one of the most easy-going, amiable, kind-hearted people I ever met. Whereas my room-mate reminds me of Neal. On the surface, he's a cordial, polite person, but once you get to know him, his constant nagging, coupled with his never-ending negativity will drive you insane.