how much more recoil does the latter have over the former?

Great answer ridge runner !!!!!!!!! Get the 45/70

I agree. 45-70 is much more versatile if you don't handload. Lots of standard ammo available if you want to shoot lighter loads, Garrett and Buffalo Bore amongst others if you want to are going after heavier or dangerous game.....or like recoil.

Garret and buffalo bore actually load the 45-70 to higher levels than the 450

Agreed, which leads to the versatility of the 45-70. I'm not aware of anyone loading the 450 Marlin in lighter loadsadequate for deer/bear, so you have to handload to get reduced recoil. Buy the 45-70.

I like the 45-70 for the fact you can get lighter loads for it off the shelf as mentioned in one of the above posts. You can also get full bore loads that will get close to 458 Win Mag factory loads. Either cartridge will take down anything you care to hunt in North America. I reload for the 45-70, but sometimes I get lazy and grab a box of the cowboy loads to plank with at the range which is something you can't do with the 450 Mar.

Wonderful responses all around so far. Thanx. I would like to further the discussion by mentioning the rifle would be used primarily as a beer rifle, as well a timber gun for whitetail and other cxp2 to cxp3 game. I also don't have the means or time to handload at this time, but will soon. I'm wondering what companies out there offer 45-70 that are not ported, or .450 that aren'tported well. I can handle a bit more energy on the shoulder versus hearing damage. I can't seem to find unported new rifles in either of these calibers-are there any?-Your feedback is appreciated.

Marlin 1895 with 22 inch barrel. It will kill any beer you find out there.

Just don't go and shoot any of my beer. I like to have a cold one now and then. As for the .45-70 and bear - every bear I shot with my 45-70 never complained and in fact didn't say hardly anything in the bed of my pickup.