Everyone wants one, until they get one. One LGS has a Marlin on the racks that he has sold 5 times. People buy it, keep it a few months before bringing it back and trade it in on something more reasonable.
With traditional loads you have approximately .45 caliber muzzleloader performance, but in a brass cased repeater. Modern loads that are only safe in modern guns do improve on that quite a bit, but with EXTREME recoil from the lighter weight Marlin rifles. If you need that much performance a 375 magnum will far outclass the hot loaded 45-70's, and do it with far less recoil, better accuracy, more effective range.
Most guys buying lever action 45-70 do so because they think they are buying an old round with a lot of history. The 45-70 round was adopted by the Army in 1873 for fighting indians in single shot trap door rifles. In less than 20 years it was dropped and replaced by the 30-40 in 1892. It was used for some hunting simply because as a military round it was commonly available at the time, but was never a top choice of the buffalo hunters of the day. It was considered too weak for buffalo by serious hunters. Marlin and Winchester offered lever action rifles for the round in the late 1800's, but they never sold well.
The round lay dormant and basically unused from about 1900 until Marlin revived the round in 1973 on it's 100'th birthday. I paid $150 for one of those original 1st year Marlins back in the mid 70's and hunted with it and shot it a bit for over 35 years before someone offered me 4X what I paid for it about a year ago.
There is nothing WRONG with the round, or the Marlin rifles. I have no experience with the others. But there is more mythology surrounding the 45-70 than most any round. A Winchester 94 in 30-30 will do anything a 45-70 will do when firing the old black powder equivalent loads and actually has more real history behind it.