Eric,
The 90's don't release very well when trying to modulate the fronts. The 01's bite hard with the initial temperature rise, then the torque curve flattens out and becomes more pressure-sensitive. The 90's are very flat torque/temperature-wise, have a progressive release when trail braking and will practically last forever on the rear.
I've run the Brakeman 3's on the rear and 3's and 4's up front. They are very progressive, but you will go through a set of fronts and 1/2 set of rears on an average weekend. The PFC's will give at least 2-3x the life of BrakeMans, so despite the higher initial price, they are cheaper to run overall.