Thank you Shelbie -- I appreciate the detailed answer. Basically, cosmetic changes, even the light position doesn't matter to me as much as the mechanics of the models. Like cars, I would like to know if there are particular years where manufacturing was better (or worse!) than others. The shorter fold up bed might also be something I would consider a factor, but wiring would be much more important to me. I would like to invest in a machine that is in the best condition possible so I can keep and use it for a long time. I'm a "user" rather than a "collector"!