From where I see it, RTWP is more demanding, if you don't want to get frustrated at the game. It's faster, more hectic, requires a higher degree of micromanagement and multitasking. It involves real time timing, sometimes even very tight timing, like under 1s in some extreme cases. You have to constantly shift your attention from one combatant to another, and can't afford to just "forget" about someone for 5 whole rounds or something. Like forget about that enemy mage who is going to drop a Horrid Wilting on your party within the next 2 rounds, so you have about 9-10s to do something about that. If the only one who can interrupt that mage is your own mage, then you have to plan out what it's going to take to interrupt that enemy mage under his 12 layers of defenses, and how you're going to do it in 2 rounds. Or forget about your mage-thief who is going to not auto-attack after casting a spell. If one round is 6s, and the casting takes 3s, you have 3s to get back to the mage-thief to tell him to do something else.
So from an angle, you actually need a higher level of understanding of game mechanics and the enemies - both enemy abilities and enemy behavior. If my character has low attack speed, it means there's going to be a delay before he can make an attack, so I should know how long that delay is. And if I have cause to suspect that the enemy is resistant to my attack (maybe very high AC or weapon immunity), I only need to make one attack to confirm that. So I'd allow myself 3-4s to do other things, before getting back to this character to see the result of that attack. I can't just "forget" about this character for 5 whole rounds, before remembering that oh wait I need to check how he's doing, then get frustrated at the fact that his weapon is ineffective and he's just wasted 5 rounds.
It's like GM4Him said, in TB you can confirm the effectiveness of your attack right away at the end of the turn - it's very simple because there's nothing else that demands your attention. In RTWP you have to keep in mind that you have a pending attack as you shift your attention to something else, then you need to go back and check the result of that attack after a couple seconds. You have to do this constantly, for multiple party members, if you want to keep your combat actions optimized.
Another example: there is an enemy mage who likes to cast Wail of the Banshee within the first 3 rounds of the fight. So I have my mage on standby and watch him, and if I hear him start chanting a necromancy spell, I have 3s to interrupt him with my mage. On the other hand, if he starts chanting an abjuration spell instead, I know it's likely going to be Dispel Magic, so I'd have my mage cast Detect Invisibility this round, to flush out the enemy assassin who's doing to backstab the hell out of my druid. To me this kind of timing and decision making is fun and exciting.
It's like multitasking, when you try to handle several things at the same time. Some players find it too much of a bother. But to me it forces my brain to work in a way that I find stimulating and fun. TB is a more "slow down and chill" kind of thing. So it's somewhat like taking a casual jog to keep your body active versus sessions of high intensity training back to back.
Totally agree with this, and especially what you say at the very end. All of *this* is what I find enjoyable, invigorating, challenging, and fun, and so by contrast TB combat comes across as lame and boring for me.