I have always had 16Gb iPhones, purely because I don't think the higher capacity models are worth the extra cost. However as time has gone on i'm finding 16Gb becoming more and more constrained.
I think iCloud Photo Library is terrible, have ended up switching it off because it went mental a couple of weeks ago and kept putting 2 or 3 copies of the same pictures on my phone. Also when I was deleting images they were reappearing by themselves from iCloud just as fast as I was deleting them! I think I may use Dropbox or Flickr apps to manage my photo backups. At least that way you can delete them on your phone and they STAY in the cloud unlike iCloud Photo Library.
Also music has become an issue, I don't store any on my phone anymore and use Google Play Music instead (which is FANTASTIC!). Install the app on your mac or pc, point it in the direction of your music folder, it then uploads all your songs to the cloud where the iPhone app can stream any of them instantly. It also has an offline mode where you can tell the app to download certain albums to the phone (just in case you are not near a data connection, going abroad, have a data cap etc) Well worth a look if you have never tried it.
Id love it if 32Gb became the base model, but I don't think thats gonna happen for quite a while yet knowing Apple.