Turn-based when leading a full party and especially when either positioning on the field or skills working in tandem matters. I love being able to give precise orders to each individual so they work well together, particularly if I've chosen skills to synergise with each other. Action rpg when controlling an individual, RTWP I don't mind so much if it's only three characters rather then five or more. Otherwise I just end up pausing every couple of seconds and juggling cool-downs rather than turn-order, and it might as well be turn-based at that point. Strategy over reactions for me, but to each their own.
If real time involves allies under AI control, it really depends how good the AI is. I quite like gambits from FFXII/Tales of Hearts R etc for at least being able to assign priorities myself.
Honestly there's hundreds of RPGs, and so many variants within turn-based (including different sub-genres) that its hard to pin down to such a simplistic rule. I like a turn-order-system, be that any of the above, that works well for the game mechanics they are paired with. The turn-based combat of Trials is nothing like Xcom or Etrian Odyssey, they are three great approaches to three different genres rather than just 'turn-based'.