I love my Husky Liners. Thing I don't like about the Weather Tech no drills is you still have a metal tab that is rubbing the back side of the fender. What good does not drilling do when your still rubbing the paint off from the back.
When I installed my Husky's I just used 3M double sided tape instead of drilling. Works really well.
Definitely function, not looks. Trucks look better without mudflaps, but if you go off road or tow a boat / trailer much, you're probably gonna want good quality mudflaps to protect your paint jobs. All of the flaps mentioned here are good quality, but also all have their flaws. Depends on your particular usage and need. I use Weathertechs when I go off road or tow my TT, when I'm not doing either of those activities, I take them off.