The high level issue is two fold. The first is preference and a lot of folks dont do it merely because they dont want a gonzo fantasy game. What do I mean by that? I mean, pocket dimensions, mass teleport, scry and fry, wish, among many others. The game changes in scope of adventure and adversary type. The second is mechanics tend to bend and break at higher levels and/or become cumbersome to run and play.
The second was really an issue with D&D during 3E. It's limitless ability stats, spells in cans, page long stat blocks, etc.. were a lot for the even high level enthusiast. I only got half way in 4E, but for a lot of folks playing for 30 levels was just too long to do. They tended to want to start over with new characters in a new campaign. 5E brought levels back to 20 and added bounded accuracy to rein in the math. Some spells were adjusted, magic items limited, etc..
PF1 obviously inherited all the limitless and unbounded math of 3E. For PF2, one of the design goals was specifically to make it easier to play high level fantasy RPG. Paizo uses a proficiency + level system. The math is very tight and the mechanics are designed were the players must work together tactically to be successful. All character abilities were silo'd into feats so character building is evenly spaced out, while giving some individual feel to each class.
Which one is for you?
Well, 5E with bounded accuracy means that everything remains relevant. Even high level PCs must fear armies of low level things. It creates a world that feels more logical in beings relation to one another. Advancement is less getting tons of +1s to offense and defense, and represented in more go power with HPs. Some of the downsides mean monsters often feel like punching bags, and are vulnerable to high level PC abilities. Which is why legendary resistances have been added to give "boss" creatures more staying power. Working as a team will make the game easier, but it isnt required to be successful. 5E, thus feels consistent in experience throughout the leveling process.
PF2, on the other hand, uses a level system. anytime you surpass a creatures defense by 10, it is a critical hit. This is important becasue it means certain creatures will die easily, and others will be invincible merely by being lower or higher level. Unlike a 5E team threatened by an army, a thousand goblins wouldn't scratch high level PF2 PCs. The interesting differentiation here is that by virtue of a higher defense, big powerful caster spells are rendered useless against "boss" creatures. The key will be working together as a team to defeat a solo challenge, making melee characters feel more important and casters lsightly less powerful than traditional approach. Unlike 5E, in PF2 if the players dont work their characters together like a team, they will be lose. Which is why if the challenge level seems too daunting, a GM ought to use moderate or lower encounters.
Pros of 5E;
More casual, game doesnt change much except a few power up spells.
Cons of 5E;
CR system is more horseshoes and handgrenades which takes practice to master. (This can be viewed as a feture as encoutner wont be entirely predictable for GM and players).
Pros of PF2;
Silo'd character generation makes it easy to level up and face the challeneges of high level play. Very accurate CR system (can be seen as a bug as it makes encoutner tooo predictable to GM and players).
Cons of PF2;
levleing up powerwise can seem less ogranic and more mechanical in nature. Facing the toughest challeneges requires a bit of system mastery and group organized thought that isnt for the casual group.