I prefer Xiaomi EU, no ads, no adware, more features, no region problems and for me battery is good.
The only "problem" is that you have to unlock the bootoader and install twrp in fastboot. If you know how to do it go ahead and give it a try, you can return to official whenever you want.
Ok Google voice activation doesn't work right now in current beta ROM, that's why I'm using 9.5.30.
I wouldn't go back to Oreo.