mct oils are antifungal, imune system enhancing, less likely to be stored then other fats, quick energy. I think antibiotik and antiviral aswell. But its not essential
Omega 3's in flax is essential, good for skin, metabolism, cholesterol. But a excess doesnt give any advantage. 5-10 grams of flax/day is plenty and get the rest of fats in your diet from mct and olive.
bottom line is dont choose, use both. But if you HAVE to choose then go with flax.