IF you don't have your heart set on any of them in particular I would go with the 45/70 just because its the most available today. If there is one you like better than go for that one. I would pick the one that "speaks" to you.
I would still like to get a 45/120 because the really long rounds are very cool and would look good in a bandolier.
Shot placement is everything! I would rather take a round of 50BMG to the foot than a 22short to the base of the skull.
all 26 of my guns are 45/70 govt, 357 mag, 22 or 12 ga... I believe in keeping it simple. Wish my wife did as well...