Time for my two cents - I have done many, many extract brews, most very good tasting if I have the patience to let them age well, and a couple of really, really good ones. I have only done one AG. It was a BIAB set up which turned out pretty good, smelled amazing while mashing and boiling, but took a while. Time is a factor in my beer brewing so I have to have a good bit of free time to do AG.
I can see the added variations you can have doing AG, but then again, with the specialty grains, extract brews have quite a bit of variablility as well.
Basically it comes down to me wanting to do more AG, but I am needing more time. Being very happy with the exract brews I've made, I think it would be fun to put it to a taste test and have some blind tastings of extract versus AG. When I was in school, some of the guys from various parts of the country griped endlessly that beef where they came from was corn fed and higher quality, thus tastier. So, we went to a local steak house and got some corn fed steaks and then to Safeway and got some regular butchers choice steaks, grilled'em and set'em out for the boys to determine which was which. We also did a blind tasting of a bunch of commercial beers.
Of the steaks, no one could destinguish between the corn fed and the safeway steaks. In many ways, I think a taste test of extract vs AG would yield much the same results.
As to our taste test of the commercial beers, we got quite a few right and we ALL got Old Milwaukie by smell alone.