ansi-term in line mode is basically the same as shell, however you still have the option of direct terminal entry with char mode, which is sometimes useful, ie

ansi-term in line mode is basically the same as shell, however you still have the option of direct terminal entry with char mode, which is sometimes useful, ie when looking at the command history of a machine you sshed to. ansi-term can also run more programs (ie some graphical programs, man).