I can tell you that with the M55 you won't have to open the door between cleanings since it has an agitator that keeps the burn pot breathing at it's peak. Sounds like the Harman may require an occasional scrape of the burnpot between weekly cleanings, easy enough. But the Harman has a better designed docking station what automatically connects both the exhaust and the OAK. The Enviro only connects the exhaust, you have to come up with your own way to get the OAK connected which could be a real pain in certain circumstances. The only reason why the M55 is a better "heater" is because it is rated for higher BTU input (55,000) vs 40,000 for the Harman. So don't let that sway you, the Harman will be as efficient as the Enviro when converting pellets to heat. Based on your climate the Harman will be plenty unless you have more than 2500sf. Neither stove will be maintenance free as they all have motors and electronics that can break down/fail. I don't think either has a better reputation as far as breakdowns are concerned. As you said, it is an investment, so I imagine looks count. I would choose based on which looks better to you or your wife. Both are great stoves.