I call it a draw. HD is making reliable bikes from the factory now, in response to poor reliability in the past. BMW was at one time THE bike to have if you rode a lot, and developed a prestige as the most reliable bike out there, but quality materials and engineering come at a price, both monetarily and in looks (1998 R1100R), Now, BMW Motorcycles have gotten so caught up in advanced technology, some of their reliability has suffered, it's tragic, really.
My 2002 BMW maintenance schedule requires valve adjustments every 6000mi. Since the jugs are flung out on the sides, this can be done with three tools carried under the seat on any level surface on Earth. Takes less than twenty minutes, especially since I haven't had to adjust them in 24.000mi (30K total). Oil changes and other fluid changes can be done by owner with moderate mechanical skill.
If you take a BMW to a dealer, though, they will charge you just as much as any HD shop. The HD shop will return your hog to you in showroom clean condition, though. Amazing chrome scrubbers, those Harley dealers.
Some things can or should only be done by the BMW dealer, like the Mototronic engine computer diagnosis, and ABS brake systems.
The "classic BMW twins" engines are overbuilt to withstand 250Kmi. Mine didn't stop burning oil until 24K. The twins also are air- and oil-cooled, as opposed to just air-cooled of HD.