Neither one is better or worse. They are different
Fish oil – Shown to reduces serum triglycerides, lower homocysteine levels, lower LDL cholesterol, and reduces C-Reactive Protein.
Krill oil – omega-3 fatty acids in fish oil are generally present as triglycerides, which are not absorbed as well the phospholipid omega 3s found in krill oil. Krill oil also contains the carotenoid astaxanthin, a powerful antioxidant.