The 38-55 traditionally suffers from an oversize bore and an undersize neck, although Handirifle's neck wasn't an issue, so maybe they've got a handle on that problem, let's hope so, there have been too many unhappy 38-55 owners, but he does need to shoot .379"-.380" cast bullets in it, hopefully he'll offer his experience on it. There's a great link in the FAQs on the 38-55 if you haven't read it.
The 45-70 BC is just the opposite, no issues at all, other than they generally have short throats, so you will need to use a bore rider bullet if you go over ~350gr, or just load em short, although that's not written in store, some have acceptable throats, I throated all 3 of mine so I could load 350gr bullets to the COL listed in data. I don't think I've ever read a negative report on any 45-70 H&R barrel, BC or Handi length. Of course, you can always rechamber to 45-120-3¼" Sharps Straight and not worry about the throat!! My 45-120 BC shoots very accurately with everything from 300gr jacketed to 555gr cast bullets. If you get the 38-55 and it doesn't tickle your fancy, you can always have it rechambered and rebored to .405 Winchester, that's what mine is after a sex change!!!
Tim