i used to be in sales for supplements and learned about them with a passion and still some now. I would like to say that fish oil and flaxseed oil do have different omega fatty acid complexes but.... Flaxseed oil contains the ALA and others that are converted by the bodies systems to turn it into EPA and DHA. You simply cut out the middle man with fish oil, but flaxseed contains the only essential omega fatty acids as the body cant make them but can make epa and dha from them. This being said as part of a "normal" healthy diet for most flaxseed is best but fish oil will enhance benefits recieved by dha and epa. Also the amount of conversion of flaxseed oil varies on your body. Some the factors that can effect your bodies ability to convert it are, lack of vitamins specificly Bs and E, having more than a little of trans fats(hydronated fats) in your diet(they intefere with many of the bodies activities hormones etc.) Another point i should make is all fatty acids including ordinary olive oil need to be extracted and stored in oxygen free atmospher, zero UV light, cold, and chemical free (most are not). If it is they will say so as it is a huge selling point to those in the know also if its really good it will be refrigerated at the store as you should at home regardless.Im sorry cant be more detailed but i havent studied supplements much for awhile and of course this is partly my opinion in what one should use.