Depends on what you are shooting. The simple answer is physics if all else is the same as other state.
Same gun, same pads, same mass down range they will kick the same.
Most high performance 45-70 rounds (non-trapdoor) put more energy downrange in 45-70....is it enough to matter to the game? I doubt it.
However, check these out from a free energy calculator online.
Assuming a 6lb gun and 45gr of powder in each (to keep it equal).
444 Superformance 265gr (I chose this because its listed velocity is higher than the FTX).
265gr
2,400fps listed
3.62 energy pulse in lb/sec (EP)
free recoil of firearm speed in fps (FRfps) 19.43
free recoil pounds (FRlb) 35.17
45-70 325gr FTX Lever Evolution (LE)
2,050fps
3.75 (EP)
20.15 FRfps
37.82 FRlb
45-70 405gr
1,700 fps
3.85 (EP)
20.68 FRfps
39.84 FRlb
For relative purposes:
12gauge shotgun held to same 6lb weight of gun and assumed 45gr of powder load
1 1/4oz of shot (547gr)
1,300 fps
3.71 (EP)
19.91 FRfps
36.95 FRlb
Edited: So the almost 3ftlbs of free recoil may not seem like much until you realize its almost a 10% increase over the 444 recoil free ftlbs?
Yes...repeated shooting of the big bore rifles are pretty equivalent to a 1,300 fps 1 1/4oz...granted shot is a bit more cushy getting excelled out of a bore but imagine that same recoil in a 1 1/4oz slug. Maybe this gives some perspective as to why the 45-70 feels like more recoil? It is. But I doubt anything on the other end can tell the difference.
RockedEm