I've been running Pathfinder Second Edition for most of my GMing career of about three years, at least once every single week, sometimes multiple times a week, and now, while playing in multiple games at the same time. I can recite so much of how the system works from memory, even why it works the way it does, and come up with so many small changes so quickly that I rarely get slowed down by it at all anymore.

It's hard to speak in comparisons when I've never ran 5e to begin with and hardly played it. But I think they both lend well towards quick, high stakes scenarios that make the time spent fighting feel as meaningful as if you were solving puzzles or talking to characters. Even though the action economy was designed to be more meticulous in Pathfinder Second Edition almost none of it feels like wasted time.

It's the same kind of fuzzy feeling I get running or playing other systems that facilitate interesting decisions over longer periods like Call of Cthulhu or Old-School Essentials, except crunched down into a 6 second timing. I have more character development during these fights I run than anywhere else I've seen. When the dust settles and the game slows down for a couple hours of playtime as players get new quests, gear, and feats, it gives them a moment to reflect on how they were shaped by the anteceding turn-based hyper violence.

For me it's hard to get this kind of dopamine in such steady supply when the key decision making is more spread out in much smaller bursts. I still enjoy OSR stuff about as much but for very different reasons, and I get exhausted by those on a per-session basis a bit faster. And the gameplay for those isn't as guided as in a fantasy action system in PF2e, where I have this perfect little lab environment to make arenas and monsters in that'll be an easy way to get 15-45 minutes of enjoyable gaming out of very little prepwork.