CB Draft. Pick 2 is more laid back, but CB Draft is more rewarding when you do something well.
CB Draft is a legitimate team-building exercise (not team as in us as a community either, team as in you build an actual team) with peer-review and concrete winners. (I don't think there are however concrete losers...more like 'non-winners'. Everyone but mgent is a non-winner.)
I'm a competitive guy, and I find it more rewarding, and it ultimately helped me find my voice here on Celticsblog.
And it really helps your basketball knowledge, and you confidence in your own basketball knowledge. Want proof? Look at Bahku flashing his teeth a little defending his team in the 'Hows my pick-2' thread. His first draft was Nick's historic draft, then the pick-2, then the real deal. By the time he was done with the CB Draft I think he was much more assertive in expressing his views and tempering his portrayal of his team, and knew what he was talking about.
Not to call him out or anything, just a guy we're all familiar with. Pick-2 is more fun, but the CB Draft is a more rewarding experience.