One After 909 occupies a pretty unique place in rock history.
It was a song that was recorded just after their first album (during the From Me To You sessions) but appeared on their final release (Let It Be) instead – a full 7 years later. The first version was released (on Anthology 1) about 20 years after the second, meaning in almost everyone's perception the 'cover version' is the original. I can't think of another song by any band that has the same convoluted history.
LIB – A raucous version from the famous rooftop concert featuring Billy Preston. The band swing the rhythm, McCartney plays a root/fifth bass line pretty much throughout. The lead guitar (Harrison) is panned right. The track ends with applause from the handful of people on the roof and Lennon sings a line of Danny Boy. There are no Spector overdubs.
LIBN – A light remix of the LIB version. Very slightly louder overall, drums louder but Harrison's guitar is panned more center making it harder to distinguish between the guitars. The track fades quickly in order to cut the applause and Lennon's comment. McCartney's BVs are lower but Lennon's off mic “ad libs” are much louder.
A1 - A composite of takes 4 and 5 recorded on 5 March 1963. The song is played in straight time, the intro is F# E B instead of B, Lennon is playing acoustic. McCartney plays constant 8th notes on bass (or tries to! - see below). Ringo adds 8th notes on the bass drum in the 'move over once' breaks.
A1 - A composite of outtakes. Take 3 breaks down when McCartney is unable to keep up playing fingerstyle. An argument ensues about suitcase between John, Ringo & Neil Aspinall. Take 4 breaks down when Lennon comes back in 4 bars early after the solo. More arguing. Take 5 is the solo till the end (but fades out early).
There's hardly anything to pick between LIB & LIBN but LIB just edges it because the lead guitar is clearer and it doesn't have that awkward fade on the end. The outtakes on A1 are hilarious and well worth a listen. The complete version on A1 is the best in my opinion, even though it clearly has more in common with I Saw Her Standing There than Get Back. The take has an energy that LIB never achieves and though the playing is equally as ropey, it's because they're inexperienced youths rather than jaded rock stars playing in sub zero winds.
Best version: Anthology 1
LIB - Let It Be
LIBN - Let It Be Naked
A1 - Anthology 1
Thanks to The Beatles Bible for background info