Basically that. If you want something super simple and 100% remote based/chromecasting then android tv work great. This is coming from someone who has successfully moved his wife over to it from a htpc/mouse keyboard combo of about 10 years.
I guess its if you want to do gaming and have well actual support and OS upgrades (if yes and yes then go shield) otherwise the mi works fine for all the streaming apps with a solid AC wifi connection. We just use the mi remote now as its CEC turns the tv on/off too. I have to manually turn the amp on but thats ok in the scheme of things