Which is better to repaint Hardiplank, exterior Benjamin Moore's MoorLife, Moorgard or Sherwin Wms Durations? This will be used to repaint Hardiplank on a garage. ...

This will be used to repaint Hardiplank on a garage. The area is 18x36 so how much paint will be needed. On most of the garage the paint surrounded by NOT peeling. Will a primer be needed?