Actually it is more of a legality issue as you legally cant have 4 head lights in most areas. So to get around that the manufactures place shields in them so they aren't not actually classified as a headlight. Seriously what percentage of fog light owners actually claim that their fog lights actually helped them out. Wouldn’t you think of it as more of a marketing or selling point rather than a necessity? From what I noticed when I went on a 1am country drive where the fog was so thick I had to drive 25 on the back country roads, the headlights were just as useful if not more than the stock fogs for driving through the fog. And I certainly would not just use the fog lights when driving through fog, it all depends on how your headlights are angled, if they are angled too far up then the light is going to reflect back up at you, this could be why it works better for some than others.
On a another note I am going to experiment with angling the fogs up enough to help the headlights more. And don’t try saying that I am going to blind some one, just look at the Silverstar headlights in the right of that picture. So KiethH, have you seen any actually comparisons on fog light modifications or are you just going by what you researched?