The main difference between flaxseed oil and evening primrose oil is that the former contains the omega-3 linolenic acid, while the latter contains the omega-6 gamma-linolenic acid or GLA for short. Omega-3s are linked to a lower risk of heart disease, cancer and arthritis, often through its anti-inflammatory properties, notes the University of Maryland Medical Center. Though GLA is an omega-6 fatty acid, which is sometimes connected to inflammation, it is one form of omega-6 that also can reduce inflammation, but is geared more toward skin, hair, reproductive and bone health. But the University of Maryland states that more research favors the anti-inflammatory properties of the omega-3 fatty acids found in flaxseed oil more than that of GLA found in evening primrose oil.