With Mi Box 4K, you can play FLAC (CD quality Audio) files via USB. For streaming, I believe both Mi Box & Chromecast, can go up to DD+. So you won't be able to enjoy lossless audio which requires Dolby True HD support.
Go for cca as it is designed for audio where mi box is not. I believe when you say cca you are refering to chromecast audio and not chromecast!! CCA can play almost any format from mp3 to high rez.
Go for cca as it is designed for audio where mi box is not. I believe when you say cca you are refering to chromecast audio and not chromecast!! CCA can play almost any format from mp3 to high rez.