Easy phone to root?

I'm looking to buy a new phone this year. I plan to buy a sim free, not on a contract phone (probably from expansys). I'm wondering what phone brands have easily unlockable boot loaders and root. I know nexus phones are easy to unlock/root, but I want to have sd card. I'm thinking Sony z 5 (i live in Japan so it's easy to buy Sony) , or possibly the asus camera zoom. Just saw Motorola x force (droid turbo 2 in us) that peaked my interest because of large battery and shatterproof screen.