@15mph, Mag about 200watts, Magneto about 210watts, Fluid2 about 160watts.

@20mph, Mag about 280watts, Magneto about 350watts, Fluid2 about 325watts.

@25mph, Mag about 350watts, Magneto about 450watts, Fluid2 about 600watts.

The Fluid2 is definitely more exponential, Mag is linear, Magneto is kind of a hybrid.

http://www.cycleops.com/products/comparisonchart.htm