Manual valve body benefits?

Yes. IMO there are benefits over an automatic valve body. The manual valve body makes the transmission shift instantly, with zero overlap between shifts. That saves clutches. They also increase line pressure. Again, that saves clutches.

About the low band apply. IMO, if you know how to shift a torqueflite, low band apply is much ado about nothing. It is to help prevent destroying the overrunning clutch when doing a burnout.

All you have to do to get around low band apply is do your burnouts in 2nd gear. Problem solved, over and out, roger wilco. People make a huge issue out of it I think just so they can have more bench racing braggin ability. "Yup that baby even has low band apply."

There's even a big price difference between them too, so if you're pinching pennies, that might be something to think about. I am sure others will flame me and disagree, but that's my 2 cents.