I think a lot of it depends on the grips. I shoot a scoped, 14" barrel w/no brake and Pachmayr grips and the recoil is very manageble. On my old-style TC with original grips I have much harder time shooting a 10" 44 mag, something about the quality of the recoil being way different.
I changed the grips on my 454 SRH from the Rugers to Hogues and the gun became a joy to shoot. After that I began experimenting with different grips for the TC and found that Pachs do really well for me.
Recoil on the 45-70 handgun is stout, no doubt, but IMO it is far less painful than hammering your shoulder with the same load out of a lever action.