PA was a large, 456 is a medium.
Not looked at the numbers but the geometry seems different- possibly as a result of the different frame sizes- the seatpost seems like it's at more of an angle on the 456, and it seems to work the fork more. Not that I'm passing opinion, it's just different.
I could be talking a load of guff but so far (after one ride!) I'd say that the PA felt 'springier'.
Currently the 456 feels too stretched out (but I can probably solve that by changing the stem) and the PA seemed easier to pedal on the flat, somehow.
456 seems to climb better though and is certainly the lighter frame.