Wiring in series cuts the voltage and speed in half at the motors. The Atlas drives seem smoother than the Weaver or MTH. I think they are not as smooth as a good single motor, but good enough for operations in most cases. I think the Atlas gears and components are machined a little finer. Also the mounting brackets have less play.
My suggestion is to get a set of axles and try it. Like you say the price is so much better. You could even try it on some regular wide O scale track to see how you like it.
Nothing on my layout runs round and round, so all my stuff has to do some work, the through trains just a little. I have some 2 motor units from all 3 mfg that have done 2 rail. Mostly because they were all that were available at the time at a reasonable price. I don't recommend seeking them out but if you have some, give it a try.
