Easily Hal Smith. For one thing, the first real of fandom is THE ORIGINAL IS ALWAYS THE BEST no matter what!
But regardless, yes, I still like him the best. Clearly he is the one the others try to imitate... Andre is trying to channel Hal, not Paul. Like someone basically already said, Paul had practically the exact same voice, but he could never totally emulate the warmth and heart of Hal Smith. Andre now is sort of the opposite... the voice isn't quite there like it was for Paul but he injects some of the same inflections that Hal had that Paul never really picked up on. Paul's Whit to me almost always just sounded really tired, where Hal was more alive and Andre is practically Whit on crack.
That all being said I don't want to diminish the contributions of either Paul or Andre... Paul is at this point my second favorite, and he really did a remarkable job considering the shoes he was stepping into... and he is the longest running Whit to date, which I'm sure explains why he is the favorite of so many. Andre of course has barely just begin... I didn't care for him at all when he first started on the Passages thing, but he has grown on me and I think improved to a great extent; although he definitely is more different than Paul was from Hal.