Nutritionally cod is leaner than tilapia and contains more of the heart healthy fat, Omega 3s. Cod is also high in niacin, B, C and D vitamins and potassium. Tilapia and cod have a similar taste, with tilapia having a slightly sweeter taste. Tilapia is also firmer in texture, while cod is more tender and breaks apart into larger chunks. Overall they are very similar and tilapia is a good substitute for cod.