I have no doubt that a display with a resolution that high on a 5.2" display will be super crisp/clear. The point I'm trying to make is Samsung is solving a problem that nobody is complaining about--can't recall ever hearing/seeing somebody say 'damn, this display just isn't detailed enough." Yet there are plenty of complaints about irregular performance. I don't think I'm going out on a limb in proclaiming TouchWiz as probably the least liked OEM skin.
If they would invest as much energy in trying to stuff as much high end spec hardware and features into developing an optimized, well constructed UI, they wouldn't need to use a supercharged CPU with enough RAM to run a laptop. Give me the stripped down yet smooth experience of the Moto X in the current S4 with even better battery life and I'll show you probably the best phone available on the market.
And just to be clear, I've owned 2 TouchWiz skinned Android devices in the past year so I'm not complaining about something with which I have no first hand experience.
The Google play edition of the Galaxy S4 will offer that stripped down and smooth experience you want. Larger battery? You can add an extended battery.
720p wasn't an issue and people weren't screaming for 1080p displays on a phone, in fact, they thought it was pointless. Thankfully, some companies took the steps to upgrade their displays and now 1080p is a standard. It offers a much more detailed and sharper image than 720p phones. Right now, people aren't screaming for 2.5K screens, they think it's pointless, yet by the end of next year, 2.5K will be the standard, people will love it, and they will also argue that 4K on a phone is completely pointless and 2.5K is perfectly fine.
personally, my Galaxy S4 runs perfectly fine with touchwiz on 4.3. But even if it ran less smoothly than the Moto X, the display is far more important to me and I would be willing to sacrifice a bit of performance for a sharper display, then for a slightly smoother performance on a lower resolution display. My priority is the visual experience. Again, my S4 runs perfectly fine, just giving out the example of what my priority is. While your priority is a smooth experience and the visual experience just isn't as important to you, which is why you would choose a Moto X over a 1080p display.
The Galaxy S5 will upgrade the display, offer a more detailed and crisper image, and the performance will even improve. Just use a Note 3 and see how smooth it runs if you haven't. The S5 will improve on all these aspects and people will get a much more detailed image of a 2.5k video then they would on a 2k/1080p or 720p phone display. They will also likely release a stripped down google play edition, not sure if they will update touchwiz or not.
For those people that don't see the visual experience as their priority, they will still have plenty of 1080p and 720p and even below HD iphones, for the people that think HD is unnecessary on a phone, to choose from. Everyone wins