I would say if u want them to be useful in fog, go halogen and if you want them for looks and longevity, go LED.
If you want to blind everyone on the road and waste money while doing so, then go HID. honestly, HIDs in reflector-fogs are nearly the worst idea I've ever seen on any forum that has anything to do w/ car lighting.. the only thing worse is 55w hids in old suvs' headlights - but most of the time u see that combo together anyway
I know those leds will not be visible in broad daylight if that's what you're lookin for. Not only that, but if you're talkin about replacing your drls (within the headlight housing), u need 9005s instead of h11 and yes you'd lose high beams. Once the outside conditions get dimmer, they'll be visible. I don't see the point of having lighting in broad daylight either way though..
I believe the audi or mercedes ones are something above 800 lumens.. maybe 1000+ even. The rating on the h11 v-led ones are 400... so if u want something bright, get more lumens
Another opinion I'll offer on this is that I don't think fogs actually help with lighting anyway. I'm comin from atlanta, which rarely has foggy conditions.. but foglights never helped me in any type of driving condition except that they act as squirrel spotters to light up road signs...
I've tried 35watt 5000k hids and halogens in the fog housing and wasn't satisfied w/ either. I'm contemplating wiring my fog's h11 halogen to the stock highbeam/drl wiring since I lost my drl to a recent headlight retrofit... or I may just get umnitza wannabes if they can be activated by the 9005 drl power output... umnitza wannabes being those led in the fog area that looks like a horizontal line...