oh I just realized you're talking about Playstation as a brand and not only PS4. Well if that's the case then I'd say third party and by a long shot.
You're basically putting Sony against the entire industry saving Nintendo/Sega/Microsoft and their 2nd party developers. Sony's internal studio stand no chance because they're greatly outnumbered. Simple as that.
If we're allowed to count Sony's "published" games as First Party, I'd still give the edge to third party exclusives but it would be a lot more comparable.