Strong Jaw is better.
Strong Jaw is better because you always get a boost, and it boosts to over 100 power. Sand Rush only stays for 5 turns, and you also have to actually set sandstorm, which can be a pain sometimes. Also, you can give fish Choice Scarf and Strong Jaw, which gives a larger overall boost if you go first. Choice Band is also good for immediate power. Also, Strong Jaw boosts other moves. Dracovish with Choice Scarf outspeeds a lot of stuff, especially if you have Sticky Webs support. Smogon thinks Strong Jaw is better too.
A good set could be:
Dracovish@Choice Scarf/Band
Ability: Strong Jaw
Nature: Adamant/Jolly
252 atk/4 def/252 spe
-Fisheous Rend
-Psychic Fangs
-Ice Fang
-Crunch