If you can find a P12 go for it, the changes to the design were to make the binding more suitable to integrated systems. The older P12 has a shorter mounting area (better ski flex) and more contact points at the heel of the boot, it's a tighter coupling of boot to ski. The PX series are excellent bindings but not better than the P series, the changes made to it were to streamline production (same heel mounting base as Nova binding) and to improve system integration, neither change benefits the consumer. The price did come down on the PX series compared to the P series so you might not save money on the P12 over the PX12. You'll be happy with either, they are both excellent bindings.