Salmon belly.

1. Taste: Salmon belly is the meat on the belly of the salmon, which is rich in fat and has a relatively richer taste, while fillet is the meat on the back of the fish and has a relatively lighter taste.

2. Nutritional value: Salmon belly is rich in Omega-3 fatty acids and protein, which is beneficial to cardiovascular health and brain function. In comparison, fish fillets are lower in fat.

3. Sustainability: In terms of sustainability, salmon belly usually has advantages over fish fillets. Some areas where salmon are farmed prefer belly fish because it grows faster and consumes less feed.