I buy the higher EPA/DHA version of Carleson's and the EPA/DHA is as high as regular Carleson's fish oil. Further, it contains a lot of Omega 3's, vitamin A and D. Regular fish oil also provides these, but near as much. I also watched a video from a reputable source, about studies on cod liver oil vs. aspirin for anti-platelet action, and it performed as good or better and was a safer option.
Essentially, the research I did and info provided by other members, indicate it is better for cardiovascular health and brain health. I only changed from regular Carleson's fish oil to Carleson's cod liver oil in the last 6-9 months. I still think Carleson's fish oil is a great product. I think cod liver oil is better but exactly how much better is anyone's guess. I don't have to take vitamin D or A as the amount is fine if you are healthy and not fighting off a cold. I have a bottle of vitamin D on hand at all times, and if feel anything coming on vastly increase my intake of Vitamin D.
Just an opinion and that of people who know more than I do. The videos I watched - I vetted the people speaking. Who they were and their credentials. If you look up studies you will find contradicting evidence which is often the case with supplements. Some show fish oil / cod liver oil increase your risk of atrial fibrillation. I take most studies with a grain of salt unless it clearly tells which product they are using. It is also possible to take too much vitamin A, but I do not supplement it other than in the cod liver oil.
As with most supplements - the studies are not always double blind controlled studies and more a collection of data available. Frustrating to say the least hence I try to gather as much info as I can, and make an educated decision and bounce it off other people who are educated in supplement use for health and preventing disease. Sorry for the ambiguous answer but if you deep a deep dive with AI or just start reading, you will probably find the same.