Multiple reports say that the ProMotion displays of the iPhone 13 Pro and iPhone 13 Pro Max aren't going to make it into the iPhone 14: while the Pro models will have it, the standard one won't. That's really disappointing, and not just because ProMotion displays are smoother.
Apple uses two kinds of OLED displays, one for the standard iPhone 13 and one for the Pro models. The Pro ones offer smoother scrolling and animation, but they also have a significant, positive effect on battery life. As someone whose iPhone 12 Pro doesn't have ProMotion and who spent last night browsing for MagSafe battery packs, I can attest that that's really quite important.
A tale of two techs
The iPhone 13 models all have OLED displays, but there's a difference between the one in the iPhone 13 and the ones in the Pro models. Those are LPTO displays, which is short for Low-Temperature Polycrystalline Oxide. LPTO displays are much better for variable refresh rates, which can slow down the screen refresh when high performance isn't needed and ramp it up when you need the speed. And they're much more energy efficient, which is why Apple uses LPTO in the Apple Watch range including the Apple Watch Series 7.
The marriage of Pro power and LPTO is a happy one: my Pro doesn't have it and I'm regularly running out of battery long before the day is done. And while the iPhone 13 does have better battery life than the 12, it's still very easy to kill the battery without pushing it that hard. And of course the more your phone can do, the more you'll do with it – so while the iPhone 14 will no doubt be more efficient, we'll probably be doing more with it too. That's enough to make me think the iPhone 14 Pro will be the best iPhone for me; if you're going for the standard model, you might want to budget for a power pack too.