Comment by gfody
5 hours ago
utf16 is more efficient if you have non-english text, utf8 wastes space with long escape sequences. but the real reason to always use nvarchar is that it remains sargeable when varchar parameters are implicitly cast to nvarchar.
UTF-16 is maybe better if your text is mostly made of codepoints which need 3 UTF-8 code units but only one (thus 2 bytes) UTF-16 code unit. This is extremely rare for general text and so you definitely shouldn't begin by assuming UTF-16 is a good choice without having collected actual data.
What do you mean with non-english text? I don't think "Ä" will be more efficient in utf16 than in utf8. Or do you mean utf16 wins in cases of non-latin scripts with variable width? I always had the impression that utf8 wins on the vast majority of symbols, and that in case of very complex variable width char sets it depends on the wideness if utf16 can accommodate it. On a tangent, I wonder if emoji's would fit that bill too..
Japanese, Chinese, Korean and Indic scripts are mostly 2 bytes per character on UTF-16 and mostly 3 bytes per character in UTF-8.
Really, as an East Asian the rest of the comments here make me want to scream.