Depends on a lot of stuff. I know one person who used to have an SP that I would take against most machines. AP, CP or even some BP's! But the fact is it depends on the machine, driver, and track. A top AP will run with a lot of other machines, just like a top SP will. I've seen GP's that can outrun some built mowers. You'll have fun in either class and depending who the two machines are racing each other that race could go either way. VERY TRUE. MY WIFES FLAT HEAD SINGLE BEAT MY V TWIN ONCE.