I'm a huge fan of both of these engine building companies. I love my Ski-Doo snowmobile but I'd also love to own a new 4 stroke Yamaha sled. I know that Rotax is primarily an engine manufacturer while Yamaha makes high end electronics, musical instruments, robotics, Moto GP machines, and lots and lots of other things. My main concern is who makes the best engines...2 or 4 stroke makes no difference, and why?