First Pathfinder. It is an OK game. It doesn't support the kind of fluid action that I like in a game and in many respects, outside of the D&D for the sake of D&D experience class/level is stifling and overly structured.
I like chases, acrobatics, action and that kind of thing and Pathfinder and D&D even with my home brew rules don't support it. GURPS has a whole lines GURPS Action and GURPS Dungeon Fantasy on the topic.
Also while I get around power creep by running Epic 6 Pathfinder , that is leveling stops at 6 with feats substitution for further advancement , simply hit point escalation is not my thing nor is the vast power differential between level 1 and say 10.
As for D&D 5e I rather like it . It still sucks for action games and has hit point creep but it basically takes care of most of the rest of the power difference. It feels like a world where Eliminster say could live in with regular people. Its quite good and designed that with luck a low level party could kill a high level NPC. Its not likely but its possible and I like that.
GURPS however is just better than either . It does action, verisimilitude and high action equally well.
Downsides well, I personally don't care that much for GURPS Magic. Now it works fine and of course I've got entire product lines that change it up anyway.
Where GURPS fails though is in bestiaries.
Pathfinder has I dunno 5 official bestiaries and who knows how many 3rd party references, maybe as many as 50 . Monsters galore
D&D 5e has one Monster Manual which is probably enough, I suspect another will be forthcoming eventually and since the system resource document and open license is released, there will be 3rd party stuff
GURPS has monsters scattered in Dungeon Fantasy, race templates and tools to make more of both but it is lacking in that area. Conversions from 3e are fairly challenging and frankly though charming the old Fantasy Bestiary is full of folkloric monsters no one would use . No one needs Agro-Pelters and Snolligosters (yes they are in the book) in their game they need far more conventional sword fodder.
GURPS is lacking in that area and I hope some means to fill that empty space comes up. It won't be me doing it though, I'm not up to the task. Maybe I'll manage a pyramid article someday though. Who knows.
The Return of Planescape? - Curious. There is a brief note on this 'countdown' at Enworld.
15 hours ago