Ok, let's go down the list to see what these "definitely better" things are -
1. FONV style faction mechanics (not just scripted gates like in P1)
Not going to comment on this because, surprise, surprise I can't force myself to play New Vegas. Maybe it's better, but I wouldn't know.
2. Numerous mechanical changes to character-building and combat (health system, everything per encounter, empower system, dual-classing with "power source," etc. etc.)
I think everyone agrees that these can backfire quite hard, nothing more to comment.
3. World is open rather than plot-gated into areas
This is just different, rather than straight up better. BG1 also has plot-gated areas (Cloakwood, Baldur's Gate, return to Candlekeep, the last areas), but it just has more open maps from the get-go.
4. Intra-party dynamics -- relationships between PC and NPCs, and among NPCs, including the possibility of companions walking out on you
It depends on the execution, if they are still as annoying as in PoE1 then this won't be better, it will be worse. Not to mention that it's not "better", just expanded. Potentially worse if they interrupt the flow too much with their pointless yapping.
5. A big city that's designed Athkatla style (districts on a bigger map, with encounters happening when moving between them) rather than Baldur's Gate style (physically contiguous districts)
Pretty much everything is going to be better than Defiance Bay, that's not an achievement. But ok, from what we've seen Neketaka is indeed better.
No idea how anyone can think this is somehow
better. It's in the different category.
Just companions with less content, which is actually a plus in my book, but I'm sure it's not in many others' opinions.
8. Day/night cycle and dynamic weather with NPC schedules
This is so trivial it hurts. It can potentially be more annoying, not better.
If this ends up true, then yes, it's better.
10. Stealing, pickpocketing
11. Completely revamped stealth mechanics
Sure, more options is better.
From all the better things, only Neketaka and better AI are truly big things, potentially NV factions depending on execution, everything else is "eh". You can live without them.