Definitely going with turn-based here.

Not only it's my opinion that it's an inherently superior system to rtwp and one of the very few things that stopped BG2 from approaching perfection.
I'm also far less confident in Larian's ability to deliver a good rtwp in general.

That said, neither option would be a deal breaker for me, as far as well implemented.
I'm far more concerned about how Larian will handle itemization frankly. Will they go the BG2 road (one of the best games ever made in that sense) or stick to their randomized loot system used in both the D:OS games, which was frankly garbage and the greatest flaw in the game?

Party control in Baldur's Gate 3 is a complete mess that begs to be addressed. SAY NO TO THE TOILET CHAIN