I can't decide which option to record videos at. Which do you prefer? I am leaning towards the 60 frames since I mostly view photos and videos on my phone but is image quality that much better on 4K?
If you have 4K screens you will probably want to do 4K as it look a lot better than 1080. If you do not, then do 1080p@60FPS. Also, 1080p@60FPS is much smoother, so just on that you may want to avoid 4K, not that 30FPS is bad, its just not as smooth. Lastly, depending on if you have the 6s or 6s+ you may want to stay with 1080p. The 6s+ has optical image stabilization at 4K. The 6s only Digital Image Stabilization, but it only works up to 1080p. So unless you have a super steady hand, 4K on the 6s will not look as good as it will on the 6s+.
Here's my thinking.. Even if I don't have any 4k+ monitors at this moment, most of my photos and videos are for Memories.. Well That means I'll be looking at these videos for years and years and I know for a fact that in 3+ years there will be A LOT more people with 4k and higher monitors all throughout their homes/offices/schools. For example, before I got married a few years back, me and my Father made a "last trip" to Dallas, Texas to see a Cowboys game and hang out on a road trip together. I took a lot of videos of our trip together because I wanted to have those memories for a LONG time. If I had those in 4k that would have been a great way to "future proof" my memories. Would you rather watch your old childhood memories on a VHS or in 1080p now if it was possible?