I don't know anything about Pathfinder but compared to even the TSR days of D&D, the culture is so much better around SJG, and it really shows in the quality and depth of the source books. They are absolutely amazing. The CIA confiscated early drafts of the Cyberpunk source book along with all their computer equipment, insisting, "This is real!" I learned so much as a kid about world religion from their primary Fantasy setting source book. The rules are very simple and elegant, exploiting the naturally occurring normal distribution provided by 3d6, which maps very well to the normal distribution of real life events and makes the plusses and minuses (or "adds" if you remember Tunnels and Trolls) a lot more meaningful, realistic, and interesting because +/-1 means something completely different in different situations.

What I appreciated most was the depth of character creation, while staying incredibly light weight. D&D always seemed like a video game where your character is nothing more than a class, some equipment and some basic stats, like it's specifically designed to produce dungeon grinds, and if you want to do anything else, that's up to the DM to figure out and mix in, but it's optional. With GURPS, you're designing an actual character in the literary sense, who has stories to explore and interests that necessarily interact with other character's interests. It's an actual role playing game.