It's a difficult choice, but I'm going against what others have posted here: go for iPhone 16!
Yes, there's the difference between 120 Hz and 60 Hz - but honestly, most people don't really notice it in normal day-to-day use.
With iPhone 16 I see a few benefits over the 15 Pro:
- you get a newer chip (which likely means longer software support)
- better thermal management (the iPhone 15 Pro is 'known' for faster-than-normal overheating)
- faster wired charging (~45 W wired vs ~25-30 W wired, and 25 W wireless vs 15 W wireless)
- lower minimum brightness (great at night or in bed)
- spatial photos
- you've only got 2 cameras instead of 3, but it's got anti-reflective lens coating which (hopefully) fixes the halos you get on 15 Pro
- QuickTake videos are finally 4K60 Dolby Vision (vs 1080p non-Dolby Vision on 15 Pro)
- You also get some other camera features, like SpatialAudio, wind noise reduction, Audio Mix (obviously you miss out on some 15 Pro features like ProRaw and ProRes, but I think for the 'average Joe', features like Audio Mix are of more use)
- More future-proofing with Wi-Fi 7
I'm not saying 15 Pro is worse. In some areas it's clearly better (like more cameras, generally more 'pro' camera tools, 120 Hz display). But in other areas, the iPhone 16 has some very decent upgrades over the 15 Pro. Like when you're low on battery, in a hurry and you have only got 15 minutes to charge, you are very grateful for the much faster charging speeds. Or when you're taking photos at night, the anti-reflective coating on the camera lenses is something you'll be happy with it. In terms of camera features... yeah, there's no ProRaw or ProRes, but the average customer doesn't use that - they benefit more from features like Audio Mix and wind noise reduction.
EDIT: Forgot the most important one! Camera Control. This is the new highlight feature. For the first time in many years, it's something new. Apple, in my eyes correctly, identified that for many people the iPhone isn't just a phone, it's also their primary camera. It likely is for you as well. You'll have the "pre iPhone 16" models and the "post iPhone 16 models with camera control".