Fot the 13pm and 14pm i actually have my storage is 256GB but as i skipped 15pm (my 14pm is still at 100% battery health, nice screen and no issues) i'll be definetely upgrading to 16pm no matter what. I usually upgrade anually so in my scenario this in an exception.
Despite running apple one family plan as a host with 200GB cloud storage i'll definetely go this time around with 512Gb version. I think it's a sweet spot for demanding video we can capture and all around not worrying running out of space with all music, podacast, movies and arcade games offline and last but not least video and photo we take (now they take like twice more storage than before and the quality is awesome)
Now i have like 160GB taken - lots of apps, games, photos and videos but no movies or not so much cinematic videos.
The 256GB is still OK, not limited for memory speed write and read as 128 GB version.
Also cinematic video are full capable with minimum of 256GB storage.
My final thoughts are price and longevity.
In general it's good buying the most storage we can afford but the details in choices may vary.
it's only my personal 2 cents contribution