Pathfinder/Pathfinder vs DnD
Higher Levels
Pathfinder goes up to level 30, DND goes up to level 20.
Pathfinder Monster ACs can be much higher. DnD tends to flatten the attack values.
Critical/Fumble
Pathfinder. The Degrees of Success in Pathfinder are different. A roll of 10 over DC is considered a critical success. A roll of 10 under DC is considered a critical fail (fumble).
Flanking
+2 flanking bonus
"When making a melee attack, you get a +2 flanking bonus if your opponent is threatened by another enemy character or creature on its opposite border or opposite corner."
Action Economy
Pathfinder uses a 3 action per turn mechanic. DnD uses a Move/Action/Bonus Action mechanic.
Pathfinder characters take a -5 penalty to each successive attack in a round
Saving Throws
Pathfinder has three saving throws: Fortitude, Reflex and Will
Advantage/Disadvantage
Pathfinder has no Advantage/Disadvantage mechanic. Status effects inflict numeric penalties
Diagonal Movement
Pathfinder has a diagonal movement penalty (geometry is real). DnD has free movement through diagonals.
Feats, Feats, Feats
Feats are big important character advancement mechanic in Pathfinder
Cleaving Finish
A feat
When you strike down an opponent, you can continue your swing into another target.
Power Creep Offset
Weapon Runes
Automatic Bonus Progression
Automatic Bonus Progression – d20PFSRD https://www.d20pfsrd.com/gamemastering/other-rules/unchained-rules/automatic-bonus-progression/
Automatic Bonus Progression - Rules - Archives of Nethys: Pathfinder 2nd Edition Database https://2e.aonprd.com/Rules.aspx?ID=2741