Hello there!
I have a Gen1 Chromecast that works great and it's enough for my bedroom.
The problems comes with the living's room TV, it's a LG with WebOS. This is the slowest thing I've ever seen. It can't even change between antenna channels quickly.
So I thought that I should buy a Mi Box S, but I don't have idea about Android TV. I'm a user with big experience in Android but none in TV version.
It would be great if you can help me. Also, sorry for my English.
Edited for lack of information:
Can you give me some advice on, for example, how much RAM is good for FullHD movies, Youtube, etc. Support for Wifi 5GHz would be great! I talk about the Mi Box because is the device with the best appearance, but i can look for others.
What exactly do you need help with? It sounds like you want to buy a Mi Box. So buy a Mi Box. It's an Android TV device. There's not much to learn about it that you can't learn quite simply by using it. It comes with a remote. Your TV isn't a touchscreen. That's the difference.