I'm going to give you a serious answer. No battle plan survives the first contact with the enemy, and one of the side effects of real-time is that your party is almost never perfectly positioned. Therefore you have to rely on your wits to adjust movement and positioning based on the fly as the enemy is doing his thing. In BG1 your game wasn't paused when you were in inventory, which meant that quick slots had real tactical meaning. You could still quaff your potions but that came with a risk.
The biggest advatange is the ability to interrupt spells with your archers. Turn-based has interrups or reaction fire, but they cannot simulate the urgency factor of moving Kivan on range and expertly shooting the enemy mage while he's casting Lightning Bolt. You can even make sure he has the time to shoot, by making him wait beforehand. On that note, in RTwP you can dodge Fireballs, again if you are aware.
Whereas traditional turn-based is more ponderous with all the advantages that come with it, RTwP is more hectic, while still having the pause to preserve that nervecracing moment as the fireball is about to hit you and you realize it's all over. I think good turn-based is proably easier to make, but that doesn't mean that it's automatically better. Hell, over the years we've seen games of both type fail at delivering what was expected.
