A lot of folks complain that the C5 acts like an on-off switch. Then you figure in the fuel mileage problems... Of the two the WS7II would be the better bet for racing. If your track is short, you may even think about the P5. A WS7II will work well on a short track too but clutch setup and pipe choice are critical. With a P5, you don't have to have an optimal clutch and pipe setup to get good performance. The only place you be at a disadvantage with a P5 vs a WS7II is the straight aways. Have a modified Top P5 and love it. It's faster than a stock WS7II though.