They are very similar, cod liver oil has less EPA and DHA than the Fish oil.
Fish Oil
EPA 180mg
DHA 120mg
Cod Liver Oil
EPA 110mg
DHA 100mg
Both are great but if you recieve a lot of sun exposure don't overdo the Cod Liver Oil b/c it has a lot of Vit. D, which you also get from the sun and a combination of both can cause Vit. D toxicity.