all the top of the line motors are awsome, you can't get much more out of them unless you have them modded, there are other motors out there that are awsome and even out of production that are as fast or faster than the 528 and OS. the novarossi 421 B was a monster, and you can find them on ebay for good $. Again in stck trim all these are very close, you would need to drive them all to see where they perform better, some one who loves novarossi is going to tell you the 528 is king and the same for Os, but to me it doesn't matter, i can get more out of either of them in about 2 hours. you also want to reserch where the motor makes it power and how long it pulls for, the OS to me pulls longer than the 528. the 528 ramps up very fast but doesnt pull longer than the Os, on a 150 to 200 FT strait the os is going to overpull the 528 period