I've got the Pro Carbon, and also a Giant TCR Advanced. The Giant definitely handles a bit better at low speed social rides (the PX is a bit jittery at the handlbars), and also downhill at speed.
However, although I prefer the Giant (particularly in summer), I never 'dread' switching to the PX and still enjoy riding it. As Cycleops says, try and get a go on one. Good luck, John.