Technical Proficiency: Giving the nod to POE2 here, as I feel like a lot of their systems (UI, and underlying mechanics) are more polished. The graphics and special effects are also better. Generally, Deadfire feels like a second game in a series, with all the resulting technical improvements therein (even if the writing failed to hold up its end of the bargain). Kingmaker has a lot going on, but could have done with a second pass in some areas, especially given the complexity of Pathfinder rules. (Right-clicking a feat and showing a tree of what other feats depend on that feat as a pre-requisite would be nice. Showing basic weapon stats when choosing things like weapon focus would too.) Graphics in Pathfinder are good, but not quite as nice as Deadfire.
Winner: Deadfire
Art Style: Depends on preference in my opinion. I think POE2 is a very good looking game. Kingmaker is a pretty good looking game, but the art style is a more cartoony. I actually kind of prefer the latter, to my own surprise.
Winner: Kingmaker
Combat: POE2's combat feels more complex and weighty than Kingmaker, but I think that's because Kingmaker does a better job of hiding the complexity under the hood. Things like shooting into combat, proper concealment, etc. Both have weather effects/terrain that matter, but I feel the impact of them more in Kingmaker.
Winner: Tie. I enjoy Kingmaker combat more but am not sure if that's more because of encounter design and recognizable D&Dish monsters/spells/feats than the actual combat systems.
Encounter design: I keep restarting in Kingmaker, so I'm not very far into it, but so far, trash mobs aside, the encounters have been way more memorable than all but a few in POE2. (Note: I haven't played the two DLCs for POE2) It's nice to see monsters I actually recognize rather than the Deadfire pseudo-versions of them too.
Winner: Kingmaker
Main story: Given that Deadfire's story was basically an afterthought, Kingmaker wins this one hands-down. I'm only a little of the way into the kingdom building stuff, but I do like the political power struggle as described far more tahn the faux colonialism situation in Deadfire.
Winner: Kingmaker
General Writing: Neither game has writing to write home about, in my opinion. Deadfire's companions are dumpsterfire bad, its introduction was awful, and the individual pieces throughout the game vary wildly in quality. Pathfinder has an unbelievable number of typos and that's-not-english text.
Winner: Non-native English speakers.
Companions: I don't like most of the companions in either game. In Deadfire, I was fine with Eder, Maia and (occasionally) Serafen, hated Xoti and Tekehu, and didn't care about the rest. In Kingmaker, I like Linzi and Amiri (a stereotypical dumb barbarian but also someone who is constantly making shit up when boasting of her explots to Linzi), don't know wtf the devs were thinking with Valerie, don't much like the Octavia/Regongar polyamorous couple, and don't care about the rest. I haven't seen Nok-Nok yet, so maybe
Chris Avellone 's contribution here will settle the score.
Winner: Solo players or those who cheat to give themselves gold and buy mercenaries as soon as they reach Oleg's.
World: Deadfire was more interesting than the Dyrwood region covered in POE1, but all the factions often felt (to me) like mere window dressing for the underlying <we're here to give you quests> mechanics. Both games have some serious lore dumps, but (perhaps unsurprisingly, given the wealth of history behind it), Kingmaker's world is more interesting to me.
Winner: Kingmaker
RPG-ness: Neither is TB, which probably disqualifies both games in some people's mind, but POE2 seemed like a very clinical affair (when dopey companions weren't constantly propositioning you on the ship), while Kingmaker does a really great job of feeling like a D&D adventure module.
Winner: Kingmaker
Bugs: Both games had significant bugs on release. Deadfire's seemed more about performance and issues with their scripting (scripts firing at the wrong time, etc.), while Kingmaker's were more about mechanics, stability, and specific story points.
Winner: My ISP, who gets to laugh as I download multiple gigs of patches
Fun factor: I still haven't finished Deadfire. I've been playing Kingmaker non-stop since release. Warts, RTwP, and questionable companions notwithstanding, I'm having way more fun with it than I did Deadfire.