I answered last year's R/C report's survey regarding "the best R/C purchase I made in the past 12 months" this way:

Saito .72

On a 4.5 lb profile with a Zinger 14x4 or Master Airscrew 13x6 Scimitar, the instant thrust is amazing. I bought it for the sound (or less of it, when practiceing TR's) but it immedately made me look like a much better pilot. As basmntdweller says, the plane will move quicker when you gun a 4 stroke than a 2 stroke will. I had an OS .46 with a tower muffler, and the Saito lets me get away with murder compared to the 2 stroke.

A friend has the YS 63, and it too is a strong runner. I don't mean to start a YS vs Saito sidetrack here, but he had much more trouble setting up his YS than me with my Saito. Part of his trouble I think is his YS won't swing the props my Saito will, as it seems to like less pitch and turns higher RPM. He likes the MA 13x5 K series prop best. A Zinger 14x4 is definitely too much for his motor. I must say that his YS .63 is a stronger motor than my .72, but I notice it's on par with another friend's Saito .82 (also swinging a Zinger 14x4). All three planes are identical models, and within a few ounces of each other)

Bigger props, glo plugs last forever, ear friendly sound, smaller lighter mufflers, amazing power for the weight and better looking (IMO). Up till now, I thought cost was the ONLY discriminator.

Interesting that jon595 likes the Webra 50 better. I'm sure the Webra is a stronger motor than the OS .46. I've not heard too many other opinions matching Jon's however. Jon, what moves do you feel the Webra 50 does better than a Saito .72 (or .82)? I think you're the only pilot I've ever met seen or heard who actually has tried both and prefers the 2 stroke for performance reasons. My saito has been trouble free for over a year now. I checked the valves once, but that was really the only maintenance I do except keeping it clean and after run oil.