Saito 4 strokers are actually quite light for thier size. Sometimes lighter then thier 2 stroke bretheren. You get more torque with a 4 stroke than a 2 stroke. This means you can swing a bigger prop. You get more pulling power quicker than a 2 stroke. Kinda like the difference between a big and small block V-8. The 2 stroke has more horsepower. It usually will fly faster than a 4 stroke. They need rpm's to make torque. Hence the rep of 4 strokers having more power.

I agree with several posters. Buy the engine that you like. Most engines out there are just fine. Supertiger's are real cheap these days. Tower is discounting them a good bit. Thunder Tiger's are supossed to be godd. I like Irvine's myself. I also like MVVS. I would not hesitate to reccomend the TT Pro or the ST in your list. Good luck with whatever one you end up with.

Mark Shuman