Both "грамотнее" and "грамотней" are correct forms. "Грамотнее" is the comparative form of the adjective "грамотный" (literate), while "грамотней" is an alternative comparative form. Both forms can be used in this context, so you can choose either one to say "write more literately."
Both "грамотнее" and "грамотней" are correct forms. "Грамотнее" is the comparative form of the adjective "грамотный" (literate), while "грамотней" is an alternative comparative form. Both forms can be used in this context, so you can choose either one to say "write more literately."