I am fairly new, well just got back into it after a few years of taking off, and now have aquired quite a few planes, and after doing much research, this is what I chose, for 4 strokes no doubt saito is the best, hands down. For 2 strokes, for the money and performance you can not beat a super tigre, they produce the most BHP and are VERY cost effective, you can get a .45 super tigre for 79$ and it is ringed and the 40 is ringed and ABC both dual ball bearings. OS of course is on the top of the list because there easy to tune and maintain, but for overall imo after learning from someone very knowledgable super tigres are the best and I put a .75 ST in my GP minnow, Saito 100 golden knight in my p-51 top flite, OS 46AX in my pulse, and am changing my evolution on my alpha 40 trainer to a super tigre 45. So IMO

4 strokes, SAITO, nothing comares but you pay alot but you do get what you pay for.
2 strokes in order of my favorites ( this is just from my opinion and from what i have learned from research.

Super Tigre ( you can get a super tigre 45 for 70$ or so and a OS 46ax for 160$ and the super tigre has more BHP but there a bit harder to tune, but once you have it set you will never have to replace it.

OS fx series
OS AX Series
Evolution

Hope this helps....I would like to hear also others input, very good post Alex....Jason