As my secondary/spare, i5S running 9.0.2 doing just fine - not chasing the newest functionality since DW & I have use of the Nexus 6 (on Fi Network) and Nexus 5X (on T-Mo)

To round off 4G/LTE coverage abroad (well, most places) - I second the 4.5" Moto-E 2015 model (XT-1521, factory unlocked) got the dual (nano) Sim Asia retail model, bootloader unlocked, upgraded to MM 6.0 stock rom, not exactly a mini rocket, but has most of "important" basic features & Apps as a backup, and with adoptive storage (whatever it's called) - 64 GB mSD card is acting like internal storage, not bad for $89 USD ... used mainly for WiFi/VoIP calling. Not bad as a throwaway, getting several days worth of standby with minimal usage & offline Map navigation (MapFactor - with updated local/regional maps preloaded).

One of my SIL has the USA model on AT&T/T-Mobile (no dual Sim) and they are definitely worth a look @ $50 shipped - she just came back from a trip down under to Aussie - and was happy with her unlocked XT 1527 (just be careful which variants you are getting cheaply ... and do not use those Sim adapters - they will jam up the slot, use only nano-sims.)