Also for me in many aspects it is superior to Baldur's Gate. Except Magic system, companions and main quest/villain, I guess.
Player stronghold : 1 very boring filler stronghold VS dozens of strongholds deepening on the player class each one with his quest and peculiarities
Ok.
Setting : I just found the Deities on PoE lackluster
Well, I've found them interesting. Refreshing even.
IMO it goes:
Side quests : Deadfire wins
Class variety : Deadfire wins and its not even a contest
Itemization : Deadfire wins
Spell quality : BG2 wins - although there are some new interesting effects in Deadfire, that fit the real time combat well (rays, walls, Combusting Wounds and such)
Spell quantity : BG2 with over 300 wins. Ok.
Necromancy : Amazing on BG2 vs non existent on PoE 1/2. Huh? You can summon skeletons as a Chanter. Drain life force with certain weapons. Greatly debuff enemies with wizard, cipher or cleric spells. Dead raw negative nergy-like damage against a Fortitude save, so... there might not be a specialization that is called there, but most of the effects exist?
Side quests : Yeah, we've been there already. IMO Deadfire wins this one.
Armor system : Nope, Deadfire.
Amount of classes and subclasses : Ehm, didn's exactly count. Anyway, Deadfire offers much greater variety and class distinction. Deadfire wins this one.
Dungeon design : BG2 wins. Hmm, Ok, I'l give you that. Some dungeons in Deadfire are very good. Just... not that numerous. Forgotten Sanctum is also a great dungeon.
Encounter design : Nope, Deadfire. Much more enemy variety. Much more ability variety. Martials are not one-tick ponies.
Writing : BG2. Hmm.. maybe.