Default [Q] Quick and easy question guys!

So I just traded my mom my GS4 for her new HTC One, and it is still on Android 4.1.2. Should I update to Kitkat and Sense 5.5 or keep it where it is?
It is an AT&T model.

What are my options as far as rooting and maybe installing CM. I'm not sure about the bootloader situation.

Anyways, I'd like to know your opinion XDA!