Unicode, of course.
If you only make websites in English, this does not really matter, but Unicode supports almost any language and encoding there, while ANSI is limited to more or less English or languages that do not have “strange letters” (for example, á, í , ö, þ, ð, etc.).
, , Unicode. ANSI, Unicode.
UTF-8 - , , Unicode, . , UTF-8/Unicode, , , ... .
(, ), Unicode.
EDIT: - , , , - . ; Unicode/UTF-8, , , , ANSI, , , .