I'd have to say both to be honest. Dugtrio's good for an attacking pokemon, whereas a Wobbuffet's more of a "tank" pokemon. If I sent a Wobbuffet out that had Shadow Tag as an ability, with Counter, Destiny Bond and Safeguard as attacks, I may not cause much damage, but I can whittle down a foe's PP trying to inflict damage and with Destiny Bond, I could take pretty much any pokemon down.
Actually, now I've explained, I'll go for Wobbuffet!
I said Dugtrio. He's a great attacker. The problem with Wobbofett is he relies on the other pokemon attacking, and if that pokemon is another in game trainer pokemon or a wild pokemon, they don't attack much. Though Wobbofett is good.
I picked Dugtrio because it's easier for me to give it a good moveset. Plus I had it in my team ever since I started playing FireRed because i hate hatching the egg in Saphirre. I could always trade a Dugtrio when I beat the game
Yeah, I'd never dream of using Wobbuffet in my team as I progress through the game, I don't have the patience for him. Dugtrio's best for all out attack and as a decent pokemon through the games, Wobbuffet's just there for screwing up your friend's team.