I've just read through all 81 pages of this thread and feel like throwing in my 2 cents (as everyone else has apparently already done)
For me, there are a lot of reasons to prefer TB to RTwP, but there are two that stand out well above the rest (and I'm too tired to think of the others right now):
1. In RTwP, I tend to get over-focused on one character or one aspect of the battlefield and get bad tunnel vision, and even if I consciously think about it I can't stop it from happening, only get burst of the broader perspective. In turn based, I end up having to go to each and every character and note how the battle is evolving for them, giving me a much easier time of seeing broader perspective.
2. TB, for me, creates many more memorable moments. to use a non-BG3 example, I've been playing Battletech recently, and in a random battle I lost Glitch (one of your starting mech pilots) to a lucky missile strike to the cockpit. Now, in a RTwP battle, that probably would have gone unnoticed or barely received a passing glance until much later, as I would be focusing on my protagonist, but here in the TB system, I got to see it happen as it did, and it really affected me. Here, this woman who lost ten years of her life to a faulty scanner's misread and now is fighting for something more than just a paycheck gets killed out of nowhere. It reminds me of how harsh and brutal the war they're now fighting is and that adds to the depth of the game for me. Will it affect everyone the same way? No, but it affected me greatly.
Also, a couple of people mention long fights. I'm doing a mental count of my playthroughs, and I can only come up with three: Goblin Fortress Courtyard, Auntie Ethel, and the dark dwarves if you choose to slaughter them. The only one that comes off as annoying in those three, in my opinion, is the goblins, since I have a simple and effective strategy for wiping them out (come out of the collapsed passageway above them and begin sniping). The other two are tense and honestly fairly difficult (especially Auntie whose doppelganger attack is brilliantly evil, though it does add to the whole drawing out thing considerably) but hit the right notes to be fun for me.
And that's three battles out of how many? Dozens? In most of the fights you're not waiting around very long for your turn, I've found.
Lover of non-haughty elves and non-smutty lesbian romance "1404. I will not spoil the adventure's mandatory ambush by using the cheesy tactic of a "scout"." - From "Things Mr. Welch is no longer allowed to do in a (tabletop) RPG"