Saito 82 $299.99
Magnum 70 $149.99
Magnum 91 $169.99

That difference is HUGE. I'd guess that price is a factor for many of us who run Magnum engines. I have four Magnums and they all run very well. I have no Saito engines. I do have three OS four strokes, and like them very much. All of them were "deals" I stumbled into, otherwise I would not have them.

cowboydfk,
the Astro Hog in my avatar had an OS 70 Surpass 1 witha 13x6 MA K Series prop. At that time I was using fuel with 10% nitro. On a grass field, takeoffs at about half throttle did not use up a huge amount of runway. There was plenty of power to do big round loops but it definitely did not have "unlimited" vertical.

My brother has a hog with either a Magnum or OS 91. He likes the performance of his plane better than he liked mine (flying one immediately after the other) but he never thought my plane was under powered.