As answered in your query on the R92 thread:
I have an H&R Handi Carbine Classic 20" that was reamed to .454 Casull and that I load for. As for a comparison of the .454 and the 45-70, as you note, the 45-70 comes in several flavors.
The .454 is the smaller .452 bullet as compared to the .458 of the 45-70 and there begin the issues. There aren't many handgun bullets that will operate at .454 rifle velocities. I use the Hornady 250 gr FTX bullet used in their factory 450 Bushmaster ammo (listed as a rifle bullet) and the 300 gr XTP MAG (mag is important because of the velocities produced).
I load the 300 gr XTP Mag at above the Hodgdon Max load of H110 for my Handi because unlike revolvers, it's good for max chamber pressures up to 65,000 psi. I have chrono'd accurate groups at 2150 fps at 5 yds from muzzle and less accurate groups at higher velocity. That is in the same velocity ballpark and bullet weight as "strong" 45-70 loads. This is a reliable 100 yd round and accurate out to 125 yds.
I load the 250 gr FTX over 26 grs H110 for 2050 fps at 5 yds from muzzle. This is below max even for revolvers because in my rifle, I found accuracy was better at slightly lower. At 29 grs H110 I got 2200 fps (5 yds from muzzle) but groups were poor. This is stilll in hot 45-70 territory, but bullet weight is low for the 45-70. I am confident with this load out to 150 yards and it is accurate out to 200, I am just not confident of the FTX at 200 yard impact speeds.
Recoil in a light single shot Handi is less than a 30-06 and less than 45-70 in the Carbine Classic's big brother, the Buffalo Classic, a heavier 32" barreled 45-70. The .454 is a sharper shove while "hot" 45-70 loads can be quite significant but tend to be longer pushes, for lack of a better explanation.
So, if you talk velocity and recoil, the .454 rifle is comparable on paper. But that misses the point of the 45-70. In stronger than Trap Door loadings, the 45-70 is artillery. It can throw 450 - 500 gr hard cast bullets a looooong way, albeit slowly, and anchor whatever it makes a bloody great hole in. Yes, the trajectory is quite 19th Century, but once a shooter figures that out, the 45-70 is death incarnate. Don't get me wrong, I really like my .454 Stutzen as a NE woods gun and bear stopper, but while the numbers may suggest some similarity, the 45-70 is another order of cartridge.
My 454 Stutzen: