Quality. It's somewhat subjective. The Japanese makers typically come out on top of the "fewest problems per 100 sold in the first 5 years" kind of studies, and brands like Harley and BMW do worse - but, it's not uncommon to find BMW's and Harleys out there that are several years old, and have a lot of miles on them. The same is true for the Japanese brands. It seems that these days more and more dealers are refusing to work on a bike that is over 10 years old, and the manufacturers no longer make some parts after the bike is out of production for 7 years. I know the Japanese do that, I don't know much about the Euro and American brands. I know that when I look at a Harley, or an Indian, or a BMW, they look pretty well made to me. I also know that the Japanese tend to have some problems with paint and pitting once a bike gets older. I have owned about 23 or 24 bikes, all Japanese and one BMW, so I can't say I know a lot about the Euro and American brands long term.