if you have a pokemon like tyranitar or hippowdon that instantly starts up a sandstorm on your team, then sand veil is the way to go.
if you don't, then use hyper cutter, due to intimidate being the easiest ability to obtain on gyarados and salamence. and both of those pokemon are really popular.
if you have a TYRANITAR or a HIPPOWDON/HIPPOPATAS use SAND VEIL
if you don't use HYPER CUTTER