Is it more nutritious to purchase GNC "triple filtered" Omega 3 supplements versus the cheap costco stuff?

The salesman at GNC insisted that their more expensive omega 3 supplements (fish oil capsules) were triple water filtered (or something like that) and are more efficient than cheaper brands. At costco however, I can get the same number of supplements for 1/3 of the price if I go with the cheapo kirkland signature brand... I am just wondering if their is really any benefit to getting the more expensive specialty GNC supplements?