But the Chromecast has no interface of it's own! If I use Netflix on Chromecast, I'm in the Netflix app on my tablet or phone. Amazon can still own it's interface.
I don't have enough ports on my TV for a Fire Stick and a Chromecast (and everything else) so I'm going to choose the one with the most options (Chromecast).
Yes, but if you're used to picking an app and casting from it, rather than picking a device and chosing apps on it, Amazon faces a much larger hurdle. On the Fire TV/Stick they control the UI. On Chromecast, they have to not only convince you to use Chromecast, but convince you to stay in their app.
They can lose a lot of users and still find it to be worth it for the extra engagement of the ones they did get.
I don't have enough ports on my TV for a Fire Stick and a Chromecast (and everything else) so I'm going to choose the one with the most options (Chromecast).