I have a Samsung Galaxy S4 GT-I9505 running stock Android 4.4.4.
I like it, because I saw a teardown of it, despite it being very compact, it looked easy to repair. Certainly as easy as one could expect for such a compact device. The battery and memory are easily upgradeable and every "fragile" part (SIM slot, USB, headphone jack, camera sensor) is on a separate, replaceable flex PCB. The parts are all available on eBay for under £15 each.
This proved useful when I got it wet, and was able to clean the whole phone by unscrewing the non-proprietary screws and undoing all the connectors. Things like the camera, USB port, sim slots, etc. are all on separate boards and come off very easily. Unfortunately the screen got wet on mine, and that killed the phone in the end (digitiser dead); however, I was able to salvage the motherboard (everything but touchscreen faulty), and used it to fix a friend's phone!