This dual reference is repeated in the final stanza (2 Nephi 20:1-4 ). There are two places where Israel can turn to avert the coming destruction. They could do as some of the others of the rebellious nations had done and surrender to Assyria, or they could turn to their God.
Isaiah is certainly not equating the value of the two decisions. It would be best if Israel were to have faith in her God. Isaiah's point is that they choose neither of the solutions that could deliver them from the prophetic pronouncements. They choose, rather, to believe in their own wisdom and strength. That pride will quite literally be their destruction.