I guess it all depends on how picky you are.
I've never had any trouble with MPC era pullmor motored engines and they run slowly enough to suit my tastes. You do have to maintain the motors, but you don't have to replace them like a DC can motor.
The Lionel 28874 has the DC can motors mounted in the trucks. These sorts of engines were made in larger production runs across a wide variety of models, so the motors are available, if not through Lionel, then through parts dealers or buying a used one to strip for parts. I find it's good to have a multi-volt type Lionel transformer for these can motored engines. I use the 1033. You can choose between the two track voltage settings for the best performance. The Lionel engines of this type do a little better on the AU setting of 6-17 volts whereas the similar K-Line engines do far better with the BU setting of 0-11 volts. For switching in a yard setting, you can get that Lionel engine to run slow with the BU setting. Or really any modern transformer that starts with a 0 setting. Most postwar Lionel transformers start off with 6 volts to the track: The pullmor motored diesels need that.
The MTH engine has vertical mounted DC can motors that are much larger than the Lionel ones I've mentioned above. I'm not as familiar with the MTH engines. I had one at one time, and it certainly didn't disappoint with performance with running. For me, the size was just too big. Mine was a horn-only engine, referenced by a "-0" after the product number. Time with tell though, how readily available parts will be for MTH products. Might be a good idea to buy a motor or two from MTH while they're available. Again, eventually DC motors just fail and stop working. Though of the many engines I have, I've only had 3 fail so far: One on a Lionel industrial switcher and 2 from different K-Line S-2's. If the motors in that are similar to other models, then once again, you could always buy a second one to strip for parts.
