I can't speak to the Yamaha...don't own one, but, I do, however, have a Honda EU3000is that I use for backup power at my home here in the woods. From an engineering standpoint, it doesn't take rocket scientists to design these things and Yamaha and Honda have all the science and engineering necessary to put together a good unit and they have been "competing" now for a couple of years in the "quiet, fuel efficient, stabilized portable voltage" arena. Quality engineering in both is apparent.
IMHO, it comes down to how well you like the design (red or blue?), the layout of the controls and faceplate arrangement and, of course, cost. I don't think you can go wrong with either. My 3000is provides backup power for my whole house (and has done so reliably for 5 years now), including the standalone freezer, refrigerator, 120v well pump, two computers and my entire entertainment system and a few lights to see with. The only thing it isn't running is the water heater (240v) and the stove, again 240v. Had a comparable model from Yamaha been available at the time I bought my EU3000is, at a significant cost reduction, I'd probably have been just as happy with a blue one
That is the one danger to "competition" in a market place. You can sell on your "name" for a while, but, when a price war starts, eventually quality suffers. That, however, is a different topic...