Actually, I think Korean is not a winner. Its block-shape dictates that a character like 이 take the same amount of space as 핥, so there's a limit on how small

Actually, I think Korean is not a winner. Its block-shape dictates that a character like 이 take the same amount of space as 핥, so there's a limit on how small a character goes. (There are fonts that try to break out of the standard square shape, but I don't think any found wide use.) I think proportional fonts have a better space utilization by their nature. Anyways, I don't think that's an important metric. It's not like we live in an age where paper is scarce.