When it comes to power it seems like D&D may have the edge, but I’m not sure. If we take away some of the limits. (IE: You can learn whatever FEATS as long as you meet the requirements, and no level cap, but base stats are max at 20) The Feats in D&D just seems more powerful. Even if you're level is capped at 20 and you can’t train yourself in another class, if you learn all the FEATS you will max all your stats easily. But Pathfinder’s Metamagic can be learned by every magic user and they have MAXIMIZE, and it well max out the power of a spell.
I do not know if I have understood you correctly, but in D&D (if you meant D&D5e since you mention the Eberron book) you have a race, stat, and pre-requirements for many feats, same as in 3.5 or Pathfinder 1e. You have way fewer feats in D&D ( you choose one feat every 4 levels, in PF every 3, and the selection is more limited), and you have to choose between a feat and upgrade a stat.
You can max your stats in 5e with feats at level 12 and above, same as in pf 1e, but in PF you are not forced to pick feats that upgrade your preferred stats, you can pick any feat you want and upgrade your stat. And you can go past 20 in any stat. Heck, depending on what type of stat allocation and race you pick you can even start with 20 in one stat.
I don´t know about the power of the feats. I mean, you need race/class features or a feat at level 4 to charge the enemies, add your str or dex to the damage of your off-hand attacks or bashing with your shield, which is something any character at level 1 could do in pathfinder.
It depends on how you define power. There are some interesting ones, like telekinetic, sentinel, etc but I miss some good caster feats. Besides war caster, elemental adept and some that add a few spells there are not many interesting ones, like the metamagic feats you mention in pathfinder.
D&D5e also has a level cap of 20, like pathfinder 1e and 2e There are no official stats for any class above level 20 besides homebrews. There is not epic levels like in 3.5, at least not still ( and 5e has over 6 years so I do not think it is planned). There are DMs that allow going past that via multiclassing or things like that but that´s not supported by WotC. Over level 20 you do not level-up per se, the DM could give you Epic boons if you want to keep playing your character.
In general, they are different game frames, they only have in common the use of the d20 system.
I am assuming you are comparing D&D5e and pathfinder 1e, if we are talking about Pathfinder 2e, it has more robust and balanced game mechanics. At least for me and my table, it´s vastly superior to the other two.
