If size does not truly matter. The full size 809 offers more design enhancements.
The full size comes with interchangeable back straps for the grips to help enable you to find that perfect just for you hand hold. It also comes with ambi controls such as slide safety, and slide release where as the compact does not include these features.
And while extra magazines can be difficult and costly to purchase, the full size magazines do come along more often than that of the compact version.
There is a dealer on GB that currently has the PT809 and PT840 listed at $259 plus $10 shipping and no CC fees. But again these are for the full size frame.