Between these two it's no contest - Bonham by a mile. Keith Moon had alot of fun moments and was a great showman, but outside of his fills...well, there wasn't really much outside of his fills. He wasn't exceptionally good at any of the basic things drummers are expected to do. He didn't keep time that well and, IMO, didn't establish the "feel" of the songs, like a drummer should be expected to do IMO, enough of the time.
Moon was a good fit for the Who ( onstage anyway )and wouldn't have been a good fit for most other bands, at least playing the style of drumming that he did with the Who.
I used the term "idiot savant of drumming" to describe Moon in a previous discussion on this topic and I stand by it. When you get down to where the rubber meets the road, going from one drum fill to another, accentuated by cymbal crashes, isn't usually gonna cut it.