RE: 2 stroke VS 4 stroke
"Dave, that's like asking who makes the best vehicles, Ford or GM. You'll get no definitive answer."
Ditto
Both OS and Saito make good engines. Both are major players in the 4S glow market and I'd consider them in the top 3. (YS rounds out my personal top 3 4S glow list.) You really can't go wrong with any of these three.