Let a metronome run to it and you will hear how messed up the timing is. Nuff said.
If you let a metronome run to Zeppelin you'll find time waivers in Bonham's playing too. Same goes for Charlie Watts and I dare say, a number of players from that generation.
It's far more than just timing where Best is concerned, I reckon. I hear a general lack of authority and drive. I think conviction is far more desirable in a player. And Pete Best just doesn't seem to have it to the level that Ringo did.