I think, for the regeneration story itself, I prefer a proper send-off. The new Doctor's appearance is often zany and jarring. However, given the choice between the last episode of the old Doctor and the first full episode with the newest Doctor, I usually look forward to seeing what the new Doctor can do. The show is about rejuvenation and reinvention as much as anything else.
But the reveal of the new Doctor has almost, by necessity, seemed to involve him acting like a crazy person trying to figure out what he looks like. It's hard to get a real sense of personality based on just that.