Avebury > Stonehenge in all ways. Though it is nice to have seen the site, the experience is very managed and packaged. At Avebury, you trod through mud + sheep poo right around a huge circle. Slide down slick chalk paths and fetch up with your chin on a giant stone sticking out of the ground. Way cool + creepy.
Have finally seen the West Kennet long barrow in person, and there will be fic to follow.