As Tim showed, the 45-70 has alot more ammo choices. You have variety too with Conley & others
with the 450, but not as much. It appears that the Horn. 350 gr. load in 450Marlin would take care of any need I would have & of course there ids the Releverution
. I believe the 45-70 is the better choice.
I have a 450 Ultra because of a good trade. I added a slip on pad (also because of monkey reach)
& it has a rod in the stock, I have thought of removing it but Mac & Tim have advised me not to
in the past, but these 2 factors combined make it a wuss.
Overall, I would go with the 45-70.