PS3 version of the game.

[Kaisha]

I was wondering if I bought it does it add 30 days of subscription time to my account?

It did for me when I added a PS3 copy to my account. I'm not certain if that was a limited-time thing around the launch, or still applies today.

Also will I be able to switch back and forth between them, I.E log out of the PC version then straight into the PS3 version on the same character?

Yes you can. You have to be logged off the character before you're able to get on the other copy of the game.

You can't transfer your UI/macros/etc between PC and PS3/PS4 though. Also keep in mind the load times and framerate in general are pretty atrocious on the PS3.