Zenfone 5 battery is ok for me. I disabled all the unused preloaded apps and use Battery Doctor but i am also not a heavy user. Typically sends mail, whatsapp, maybe 20 mins of call per day and occasionally Line Calls.surf the web about 30mins and read articles from preloaded docs on reading mode for 10-20 mins.usually can last whole day.
Redmi update is mainly MIUI and not sure if will go kitkat but believe Zenfone will. Note that Redmi is not 100% english. I bought 2 few months back for my mother and MIL and therevare still chinese somewhere inside.
Redmi camera is snappy compared to Zenfone 5 and Zenfone 5 flash is lame.
However, I choosed Zenfone bcos it has 2*3G slots and i felt it didnt hurt to have 1 extra GB of memory. If there is no additional memory, i may have given up after the delay.
If you want long battery life, none of this phone will be considered good compared to other flagship models but for a utiliy phone I think it works. Similarly, for the camera but both are good enough.
Maybe future upgrades will improve the flash of zenfone since flash lights seems to be capable of generating more brightness.
Probably the best part of using these phones is that you are not a follower chasing after big brands and dare to try.
At least now I have tried intel chips. If there is a amd coming out, I may try it too.