If you're using RtwP, don't you frequently pause the action to tweak the behavior of individual party members? That's turn-based in a nut-shell. If the AI is fairly sophisticated and you don't need to control the action, then you're mostly just watching the action anyway. Where's the fun in that?
The turn-based and real-time with pause approaches both have their pluses and minuses. But the greater the number of units you need to control, the more beneficial (even essential) turn-based becomes. This is because you're trying to simulate the decisions of a large number of thinking creatures, which is pretty difficult to do in real time.