I have a R.O.W. B&O originally purchased new, and an old KTM factory 3 rail version (manual reverse). Both are nice models. I do not have a MTH but have seen them. I won't remark on the KTM as they are a fluke to find 3 rail and they have no reverse.
The R.O.W. has fully detailed valve gear, The MTH has simplified cheapo valve gear.
The R.O.W. has more detail in general as would be expected in a brass model, The MTH is a starter engine with much less detail.
There has always been something about the front cylinders of the MTH that doesn't look right, even though I can't put a finger on it exactly.
The R.O.W. has electronic F-N-R control as was normal for its time. I do not know if the MTH has DCS or not.
I have have not seen where Atlas got the tooling, just going by what market Atlas is going after, I doubt it.
Below are my opinions:
Cosmetically there is no contest as R.O.W. comes out on top, putting a control system in would require a "tag along electronics" car to house the components. Depending on the MTH control system that would be the only advantage in my opinion if you can tolerate the cosmetics. If someone wanted to tinker, by adding details the MTH could probably dress up fairly decent.
So how you operate could make a difference and what you can tolerate cosmetics wise. I'm not a rabid rivet counter, but the MTH just never cut it for me, but remember it was never intended to be a premier line locomotive.