Default Need advice for a new top

Hi, i have to buy a new smartphone, i need a lot of Storage memory, easy root and unroot process with possibility to reset to stock and send the device for warranty, good game performance and compatibility, i'm thinking Google Nexus 5 32gb, Xperia Z1 or Xperia Z Ultra.
I read that on Z1 and Z ultra users can't move app to sd without root, will they implement this feature?
How does the google against rooted and unlocked device, there is a way to return stock, or obtain root privileges without unlock and touch anything, with all stock and continue receive ota?
Previously i've rooted my n7105 with framaroot, no counter flash, with this i was able to unroot easly with app, receive ota and restore root, without touch anything of stock, i'm looking for a similar experience device.
Thanks to all in advance!