Must refrigerate Flax. I purchased it once, but only once, because of the price- it's too expensive.
The main advantages of olive oil are the likelihood of decreasing "bad" cholesterol and blood pressure. For our purposes, it is quite cheap, compared to Flax and Hemp, with 120 calories per tablespoon. Mind you there is also 14 grams of fat accompanying those calories. If you could afford the Flax, go with it, but considering how much money you are probably spending in this game- supplements, food, gear, etc.- I would think you'd want to spend the least amount of money as possible.