And to actually answer your post.... and these are my opinions and mine alone.... By order of preference of best F seats

738
757
M80

The 75's have the old leather chairs, but they are wider than the M80's, so that wins for me.... not that I'm all that wide, but still... And there is IFE. No such animal (or screen) on an MD80 unless you bring your own.

As for United, their 757's do have video and most have the "empower" power ports. Their 737's have audio, but no video that I've seen.