I have heard that the STS 30 has the power over the high end engines, its just you have to baby the STS engines for about 1 - 1 1/2 gallons. and you have to that long on $400+ engines. I heard that the rb928 eats fuel really bad to go with the 728. the lrp 28, I heard its a SH engine, that I would go with the sts over the lrp. the ninja I heard alot of good things about it. but I would pick either the STS 30 or the Novarossi 528