Depends on type of sushi.

These days there are sushi where you put ponze sauce on it instead.

Since there is already a base of vinegar in the sushi rice, so soy sauce is a good match.

Most of the places we go to in Japan, already add the wasabi to the sushi so adding wasabi to the soy sauce is overkill.

Generally speaking, I like to dip it into a little bit of soy sauce.