Beyond that, purchasing one will give you access to the other two versions (cross-buy) and saves will be shared across all three devices (cross-play). So, if you happen to own all three platforms, you can pay for the game just once and be able to play it on any device and pick up where you last left off due to the shared saves.
The PlayStation Blog entry for the game also mentions that 3D will be supported on the PS4 version of the game. It will also run at 1080p and at 60fps on the PS4. The PlayStation 3 version will run at 60fps as well, but only at 720p.
