They are far more versatile all around guns than AR-type firearms, especially from the perspective of someone who handloads and casts his own bullets.
Are you saying that with the proviso that I can't change uppers?
Even if we assume we are only putting one upper on an AR type I'm not sure that I would agree that a .357 lever gun is more versitile than an AR in any number of cartridges. I say that as someone who hand loads and owns a .357 mag lever gun (I even have a very large chunk of land where I can shoot it.)
You stated versitale, not economical and as such I'm speaking only of versatility at this point.
What can a lever gun in any of the cartridges you mentioned do that a 300 BLK AR carbine wont? I can think of a few things. Share ammo with a sidearm, be used in CAS (the AR instantly evens things out though by being competitive in 3 gun where a lever gun wouldn't be). Beyond that what? And cartridges like the 300 BLK, 6.8, 6.5 have the numbers ballistically speaking of any of the cartridges you mention. Furthermore, as much as I like lever guns the AR with its modularlity and ocean of aftermarket parts makes it pretty dang versatile. You can have quality QD mounts and go from Irons, to magnified optics, to RDS, quickly and easily. Heck you can even have all three on the gun at once. If we listed every plausible possible task for a carbine to do, do you really think there are many that an objective person would chose a 357 lever gun over an AR in 6.8 6.5 or 300 BLK for, let alone name more than a few very niche tasks the AR couldn't do?
For an all round gun I'd actually argue a 6.8 or 300 Blk AR would blow a 357 (or any of the others mentioned) lever gun out of the water.
Hunting: Some states such as IN might limit you (of course a 458 socom is still on the table for the AR), but with no artificial limits a I'd take the 6.8 or 300 BLK. More range, more energy, and more accuracy.
Defensive use: I like lever guns and a lever gun can still be a fairly practical defensive tool. That said, this task is unquestionably the providence of an AR.
Gun games: There are some such as CAS that you would need the lever gun. Overall an AR is more useful in a broader range of gun games. In any of them if you really want to compete you are likely looking at getting equipment that will fall outside the purview of a general use gun.
Fun/recreational shooting/plinking etc: One would have to run the math for a hand loader as to cost. That said IMO and experience they are all guns and can do this task and be pretty good at it. Shooting at distance the lever guns will fall on their face a bit where as a number of AR calibers are good for punching paper out a few hundred yards.
Ability to mount suppressors, various optics, etc: AR hands down
Some times I'm sort sighted, so I would be interested in hearing what the tasks there are that a pistol caliber lever gun will do that no AR type will. I just don't see how a lever gun is more versatile.