The pressurized fuel system makes it easier to mount the tank in the wing..but lots of profile flyers like the tank to be visible. Also, an 8oz tank won't fit in the OMP wing without modifications.

Judging by the RPM figures I see, I think the YS is marginally more powerful (Constrictor has a Saito 72 and a YS 63 and says he notices no difference). The YS gets worse fuel mileage and needs 20% nitro to perform at its best.

I think if you are asking these types of questions (no offense, no harm in asking questions!) that you might be happier with the Saito. I love YS engines, I own only a couple of OS's and one of them is on Ebay right now...so basically all my 4 strokes are YS. But I'm a total gearhead, tuning engines is instinctive to me. If you are new to 4 strokes, the YS might be a bit overwhelming as a first 4 stroke engine. I just think the Saito would be a better choice as a "plug and play" engine. The YS demands a very exacting set up and tolerates very little deviation from this set up. Once properly set up, however, they are a joy to operate.