One I only take fish oil which are certified by IFOS. Manufacturer can said they are the freshest,no contamination, blah blah. But do they have proof to prove their claim? A fish oil manufacture which cannot produce a certificate of analysis (email them for it) should start ringing some alarm bells as they have something to hide. IFOS is 3rd party.
Second, IFOS certified both ethyl ester and triglyceride fiah oil. I only take triglycerides fish oil as they are much more stable (won't go rancid so fast), better absorbed and exist in nature as triglycerides. Ethyl ester fish oil are cheaper to produce but more prone to oxidation (bad thing) and is less absorbed by the body.
Third, their DHA-EPA contents are pretty high when you compared to fish oil sold in malaysia pharmacies. (you need lesser softgels to meet the min amount per day)
In the US, Nordic is like the gold standard for fish oil. If you money is not an issue to you, take Nordic.  If you are on budget, take Carlson.

Hope this answer your questions.