Tough one. DAO has better standouts, but DAI is more balanced. DAO had more "freedom of speech" during quests (I never cease to be amazed at the back-and-forth the three companions have over releasing Jowan without the Warden saying a word or the many variations of the prison break), but DAI has better cutscenes (Cassandra flipping the table on Varric was golden).
All in all I liked the not-so-snugly, underdog team dynamic in DAO more, it gave way more tension to disagreements even if no one was killed (which could happen). DAI was too easygoing fluffy fantasy in that sense for me, despite the supposedly Earth-shattering conflict going on. Everyone being confined to a tiny camp also added more to the homey, "we are doing this together" feel than the vast halls and many rooms of Skyhold, though this is more due to game design reasons than anything else.
Furthermore I think general exposition through the characters was handled way better in DAO. As many additions to the lore as DAI has, most of that was exiled into long-ass texts and random codex entries instead of making NPCs tell you the gist of them. Yes, there's Solas with the spirit babble, Mother Giselle with the Chantry babble, Cole's insights etc. but nothing particularly new or intriguing. Dorian hardly shares any Tevinter lore we didn't know already, the only one who is actually interested in Ancient Elven lore wouldn't talk about it (heck, the ones who actually did were the returning Morrigan and Flemeth), Iron Bull barely delves into Qunari customs, no Chantry person seems to care about what Cory said of the Black City's empty throne, the list goes on. I found these baffling, for it wouldn't have been much effort to remedy these.
DAO wins.
Sorry DA2, I could never connect with a single one of your lot.