According to , the Agency for Cultural Affairs () conducted a study on this topic and found that 69.2% of people used to someone of a higher rank vs. 15.1% for . To someone of a lower rank, 53.4% used , vs. 36.1% for .
So I would conclude from this that it is safe to use to someone of a higher rank, whereas should probably be avoided. seems to be used more in either case anyway.