I can't remember the last time I used a non-ascii character in the terminal. I know that's not the case for everyone, and they deserve good terminals too, but it does mean that the criteria measured here have no relevance to my choice of a good terminal for me.
Seems quite hard to avoid
- file management such as running "ls" where any filename has any non-ascii character such as a CJK or accented letter
- editing any text file in a terminal editor that isn't 100% ascii
- viewing/printing any data from any source, such as a log file/the web/'curl'ing something, where any language other than English or non-ascii character is used
- using various modern command line tools that insist on printing emojis in their output