If you plan on hardcore racing, are on a budget and one motor is going to have to suit all your needs, I would say go big, there is no replacement for displacement. You can always "cork" a bigger motor to accomodate smaller tracks, but there is only so much you can do to a smaller motor to get it to run with the big dogs on a bigger track. I do agree with Roscoe, it all depends on your track, might I add budget. If you plan on racing at one track most of the time, then get a motor suited to that place. All the motors mentioned are great motors Don't buy those $100 motors!! It's worth scraping up the extra cash and shelling out for the high end motor once, as opposed to buying a cheaper motor often. From my limited personal experience, I have learned many things, and one of those is that you get what you pay for....