Bit vs. Boolean columns

Personally, I would use the BOOLEAN for a boolean value. But keep in mind the caveat that in MySQL, BOOLEAN is just a synonym of TINYINT(1) [src].

This, of course, means you can have values other than 0 or 1 if you are not careful. To avoid this, you can use the aliases TRUE and FALSE when inserting and updating data, as those map to 1 and 0 respectively.

For the sake of being complete, prior to 5.0.3, BIT was also a synonym of TINYINT(1).