I’ve heard that 1e and 2e are very different games, but I haven’t played 1e. What I like about 2e is the consistency of mechanics - for example, pretty much every spell and effect with a saving throw has results based on whether you rolled a Critical Success (10+DC or more), Success (>=DC), Failure (<DC), or Critical Failure (DC-10 or less). This applies to attacks as well, any time you roll 10 or higher than the enemy’s AC you get a Critical Hit which doubles the damage you deal. There’s also a standard set of conditions that all spells, special abilities, etc. draw from that are clearly explained.

I don’t have any serious experience GMing 2e, but everyone I’ve talked to online says that the encounter math is extremely well thought-out. Whereas some TTRPGs value simplicity, or the player power fantasy, or any number of things - diversity is the strength of the hobby - PF2e’s focuses are balance and consistency. You can still have a ton of fun in PF2e (I smile when I think of the time my three party members and I held off no fewer than thirteen enemy bandits in one frantic combat), but you can reliably expect two parties at a given level to be about the same power level, building your encounters accordingly. A big part of this is the fact that rolling for stats is a variant rule rather than the default. You get fixed bonuses to certain stats during character creation based on your ancestry, background, and class. Your health starts at a number based on your ancestry, class, and Constitution modifier. Your health goes up a fixed amount every level based on your class and Constitution modifier. And finally, the full multiclassing system that exists in D&D is replaced with the Archetype system by which you can pick a feature of another class, or just favoring a specific playstyle, every time you get a class feat. (A popular variant rule that a lot of tables use is the Free Archetype rule, where you get a free Archetype feat in addition to your class feats. Helps spice up the build variety without letting things get out of control.)

If you’re curious about playing Pathfinder Second Edition, you can read all of the rules text for everything they’ve ever published on Archives of Nethys for free thanks to a special partnership Paizo has with that site and the very permissive license that Paizo uses. Foundry VTT also has legendary support for the system. If you like books, you can buy PDFs for a steep discount on Paizo’s website.