I have ran all three engines on the same plane. The OS 91 Surpass ran a little better than the Saito 91 (better throttle response, fewer dead sticks), although the Saito did have a better idle. I used 15% fuel, 14 x 6 prop and an OS F plug. The OS would pull the plane vertical a little better than the Saito, in spite of the OS being heavier. The Saito used quite a bit more fuel than the OS. I adjusted both engines to run about 300 RPMs below peak.

The YS 91 outperformed both the OS and the Saito in all categories. I used a 15 x 7 and 16 x 6 props, 20% fuel and an OS F plug. The YS used fuel at about the same rate as the OS. The YS idled better, had better throttle response, pulled the plane vertical a little better than the the OS and had less deadsticks than either the Saito or OS, especially when flying inverted or with the engines at idle speed. I think the YS is about 4 ounces heavier than the OS.

All 3 are good engines. I favor the YS, especially the pressurized fuel system that keeps the fuel mixture constant throught the flight. You can also mount the fuel tank on the CG, so the CG doesn't change as the tank empties. The YS also does not have a breather tube on the crankcase to contend with. All 3 engines are similarly priced within $40 or so.