Hard for me to give an opinion on these types of device because I personally don't see enough value in them. The iPhone is a much better at all of the things a music player does plus of course it does a lot of things a music player doesn't. You don't need to use the extra features but they are there if/when you want to use them. Also the screen on an iPhone is larger and higher definition.
The ONLY thing these players have is larger memory..in terms of additional card slots which of course the iPhone doesn't have.
An Android phone on the other hand has all the advantages of the iPhone with larger storage as a bonus.
For example you can now pick up a Huawei P9 with 32Gb on board for less than £100. The microSD slot will let you add a further 128GB. It also has a USB Type-C port for fast charging and a nice large 5" HD display. Oh and it has duel 12 Pixel cameras that produce excellent photos...if your into taking snaps of course.
So when you have that kind of value for money product out there vs a single function device like a music player I have trouble assigning value to the latter because I see so much more value in the former...if you see what I mean?