Bonzo, simply because he had such great influence. Beauford is obviously the guy with more technical ability, but that doesn't necessarily make him a better drummer. What's he played on?
Bonzo more or less invented a style, and gave his band a distinctive sound. He composed drum parts that defined the songs he played on, much as Ringo did, before him.
There are a lot of very, very technical musicians out there today who can play lots of stuff that neither Bonzo nor Ringo could play, but none of them are Bonzo, and none of them are Ringo. (or Moon.)
These definitive drummers are not to be F'd with. I'm sure Carter, and a bunch of other guys have taken drumming to a whole other level, and that if Bonham were still alive, he'd be a huge fan, but the question was "who is a better drummer?"
For me, it's Bonham by a mile, no question.