I voted for Bashasaurus.
I used to have both of these vehicles as a kid, and from what I recall of their sizes relative to each other, I think Bashasaurus would have the distinct advantage. It is slightly larger (again, from what I recall), and it could use it's giant ball to smash the Landshark to smitherines.
While the land shark is a cool, dangerous vehicle, it seems like it would be more useful against opponents who are either not in vehicles or are riding very small vehicles. The Jaw and teeth of the vehicle really wouldn't be able to open wide enough to do any real damange to the Bashasaurus. At best it would maybe cause some scratches to it's surface... which would not be cosmetically pleasing to the eye, but wouldn't actually stop the functionability of the Bashasaurus by any means.