Per RAW, there is nothing that says it works any different than any other trip weapon, so it would thus be a CHOICE between tripping/doing damage. Of course, that's stupid so I would never rule that way myself.
Further, 'ranged trip' or 'ranged combat maneuver' is nowhere defined, and since the rules go out of their way to SEPARATELY define CMB checks, instead of just describing their differences from normal attack rolls, there isn't actually anything directing you to use your DEX instead of STR for this ranged trip attack. Again, that's stupid so I would rule otherwise myself.