I would rather a 1958 Duo Glide Flan, but my pick is the 07 Streetbob, old school look with modern reliability and no oil leaks.
I dont think that there is just one. It depends on what you want, long distant cruising, or just going around the corner bar hopping with mates, or finding a road with lots of corners and hill. I like the look of the old Pan and Knuckle motors though, and they do sound good.
08 Street Bob