I recently switched from riot android to riotx, and while it is indeed beta quality in my experience that is more due to some missing features compared with riot android (such as VoIP, searching rooms by name, and sharing files) than the stability and usability. I still have riot android on my phone, but I haven't opened it in a week or so.
If the missing features (that are clearly being worked on and probably will be implemented soon) are not a big deal I would highly recommend to start using riotx!