To maximize the benefits from the nutrients you're taking, you need to absorb them well.
The reviewed research is interesting because it investigated how well fish oil was absorbed(Beckermann B, et.al.1990). The study was a so-called crossover trial. This means that the same participants ingested different kinds of fish oil, which were compared to see if there was a difference in how well they were absorbed.
Three forms of omega-3 fat were compared, and the amount of EPA/DHA (the active ingredients of omega-3 fat) were measured in the blood after the participant ingested capsules containing different forms of omega-3 fat.
The most common form of fish oil is ethyl esters because it is cheaper to make, so that was included in the study. Also included was free fatty acids.
These two forms were compared with a triglyceride form.
The free fatty acid form was absorbed the best, but free fatty acids oxidize very easy which means they get rancid very easy, so it is unlikely that you will find that form as a supplement. The triglyceride form is the most stable form and the study documented that the triglyceride form was absorbed 50 percent better than the ethyl ester form.
It is more expensive to produce fish oil in a triglyceride form, but you don't have to pay 50 percent more for a quality product, so the triglyceride form is a better choice.
Beckermann B1, Beneke M, Seitz I. [Comparative bioavailability of eicosapentaenoic acid and docasahexaenoic acid from triglycerides, free fatty acids and ethyl esters in volunteers]. Arzneimittelforschung. 1990 Jun;40(6):700-4.