That's like asking, would you rather be ruled by a Democrat or a Republican administration? Or Tory or Labor?
But, I guess my vote is for the Grizzly. You probably get a bit more warning, and you both are equally at home on land. You stand some (but slim) chance of escape.
With a shark, you probably have no warning, and they are masters of the water, while you are a floundering potential snack with no chance of escape.