Agree with all the others about teriyaki over straight soy - in a pinch, for a quick and easy teriyaki sauce, combine equal parts soy sauce and sugar, plus garlic, fresh ginger, scallions and cornstarch slurry to thicken.

Teriyaki does have more layered flavor. It's easy to overdo soy sauce and wind up with a very salty concoction.

If I had to choose between the two, I'd choose teriyaki; I usually end up making my own similar to nutcakes' idea above. I find straight soy sauce awfully salty, even the reduced-sodium kind.

I'd go with the terriyaki. Soy alone is a little one dimensional. I use soy sauce with chicken stock, oyster sauce, chile sause and sherry if I have it. Thickened with cornstarch and water slurry.