PA1000 Thin metal plates bonded under keys, small key improvements.
1000 Buttons Plastic...700 are rubber.
1000 Better larger Mid-Bass unit with separate dedicated tweeter
700 has smaller concentric Mid-Bass unit with small tweeter dome.
1000 has larger memory for Sampling.

Pa700 is best value but Pa1000 for me is worth paying extra because hopefully the many years of ownership the difference is minimal.

Careful I may be talking myself into a purchase...Ha!!!