Roku is great and can now be controlled via google voice. I have used and tested numerous Roku products for the company and all have worked well. The only time I had an issue was when certain channels within the roku stopped working, a quick email to their support and I had those channels back within a few hours. An inconvenience for sure, but their support was always on it.
I have only used the fire stick once and never got to Cullen explore its use so I can speak for that.
The chromecast is a pain because you cast your phone to it and you may not always want to do that, you may just want a stand alone device which can be controlled a number of different ways. I have also experienced signal interference when trying to cast a movie, so there is also that.
So recommendation would be the Roku