well i rooted easily from kingroot. and i dont know if g and a versions are the same in performance. but one thing i can tell you for sure: it is way better! very easy to handle, beautiful design, very good multitasking drawer, better than flyme 4 have which is realy crappy, settings in the notifications bar, and on and on. and if you updated and you are not satisfied, you can allways downgrade.
ps: even if its slower, you can do things faster with the os being very good made.