If money is not an issue, go with the Saito. I own the FL-70, and it really is lacking in power. I blame the air-bleed carb, but what do I know? I'm just a dumb pilot!

The FL-70 is the rear engine on my Cessna 337 Skymaster (push/pull) and I have a Magnum on the front. The O.S. is more quiet but clearly less powerful.

If the Saito's price bothers you, the Magnum is an excellent 4-stroke at the same price as the FL-70. Magnum is powerful, reliable, smooth transition, etc. I couldn't be happier with it, personally... I can't speak for Magnum's 2-strokes due to lack of experience with them, but their 4-strokes are doing much better these days than in the past.