The legacy setup has larger diameter rotors (as they require 17in wheels). Larger rotors with more mass, so better brake modulation along with more mass to absorb heat when driving hard, reducing brake fade.
I'd also wager to say that the 2-pot setup has more brake torque than the 4-pots, as the WRX 2-pot calipers have more brake torque than the 4-pots.
It would be equivalent to a cheaper BBK alternative for the WRX.
These would probably make a mean Auto-x setup...lighter weight than a stoptech or brembo setup. Would give you the same brake modulation as a BBK and better fade resistance than a stock setup.
And I'll say it again, BBK's don't make you stop faster. They just absorb/dissipate more heat than stock setups allowing for more repeated stops w/o brake fade.
I'd drop my 4-pots in a sec for this if I didn't want to stay on 16in wheels.