(Note: using the key of C major as generic instead of roman numerals.)
Yesterday I was reading the book "Hearin' the Changes" (by Coker, Knapp and Vincent), which discusses Fm7-B♭7-C as an ubiquitous formula called "backdoor cadence" used to return from tonal centre F to home key C.
However, the New Real Book's sheet for All of Me, for example, has F6-Fm6-C (measures 25-27).
Both formulas seem very similar in purpose (return from IV) and chords used. Both sources seem pretty reputable.
My question is: after an F chord (typically F triad or F6) established as tonal centre, which chord, Fm6 or Fm7, makes more sense to you? Why?
My own thoughts on this don't amount to much. I wonder if maybe Fm6 makes more sense when B♭7 is omitted and Fm7 makes more sense when B♭7 is present. However, I'm unsure about the use of Fm7 because generally I haven't seen the tone E♭ (or D♯) appear much at all (blues aside, such as in IV7 and ♯IVo7).
I'm particularly interested in the use of IVm in jazz standards, but any comments will be appreciated.