Both, but with a fairly significant edge towards third party exclusives, especially if you consider their "second party" developers (namely, Insomniac) as third party.
As a huge JRPG fan, you can't compete with Playstation's third party exclusive JRPG line-up. The aforementioned Insomniac also gave us the good Spyros and Ratchet and Clank.
But at the same time, Sony's first party gave us The Last of Us. And that's pretty much a good enough reason for me, despite me not being a fan of a lot of Sony's big first party exclusives, namely God of War, Gran Turismo, LittleBigPlanet, and Killzone.