Very difficult to answer. In these instances I usually go with "I Am The Walrus". After all these years I still dig it immensely.
The tempo and Maccas base lines are very catchy.
There is a school of thought that says Paul does not play bass on this track. Now I don't have my books or anything with me but it goes something like this - They recorded the basic track with lead vocal live. This was during what I call Paul's Piano Period - you know, around Revolver or so he really hit that hot streak of piano-based songs. So, Paul's playing the keyboard and singing so he can't be on bass because apparently the basic is all on one track performed live (no bounce-down). That leaves either John or George. I'm guessing George. Sounds a little too "involved" to be John to me. Plus I seem to remember that John was doing something else that prevented him from playing bass - maybe percussion, or maybe he wasn't even there.
Anyhoo - again, this is all from memory. I know it came from the Lewisohn book plus some essay in the 910 or something. So these are not stone facts but I believe they point the way to The Truth. I just do not have the time to find it right now.
BTW, I've been lurking for about a month. Nice place you got here. My name is Pete but "DV" is fine too. Less letters.