It is hard to answer this without looking at particular wheels. Assuming aerodynamics are the same then the light wheel is going to be better. Now for example you take my two expensive wheelsets, the carbones and the race x lite aeros. They both to 40 grams weight the same but the carbones are much faster at speed... aerodynamics play a big role. If you were acceleting from about 10 MPH then the lighter wheels would be better, but at race speeds... 20+ MPH the aero wheels will be faster...