I know your question was aimed at Gary, but I'd like a stab at your question.

I don't think you could compare the Manum to the Saito. It would be like comparing a Saito to a YS.

I personally really like Magnum engines. They are really comparable to OS. If you are competition minded, the Saito would be the better choice. It is a lighter engine and does not have a piston sleeve. They chrome line the bore. This save a lot of weight. Both are VERY reliable.

The only other question is how much can you afford. High performance comes with a hefty price tag too. If you are not worried about the money, go YS 1.10.
Otherwise the Saito has a much stronger thrust to weight ratio and you will get more out of it than the Magnum. Not to mention the added C.I.D.

Brian