Jane, thinks for the trick question.
Most folks would talk about performance gain i.e. per lb of thrust per pound of fuel per hour. I have a tendancy to match this up with the mission.
I'll take the pressure ratio increase as my better performance improvement, that way I can do what I want with the inlet pressure/temp to the turbine, depending on how big a fan I've got and what I'm using the engine for like a fighter jet or a loirtoring sub chaser. Then its a matter of torque out of the turbinefor greater mass flow out of the fan or jet velocity out of the turbine exhaust for high speed manuevers