I just got back from my first trip to Shikoku this weekend. We drove down from Tajima and did a day in Tokushima and a day in Kagawa. I can't offer much help on the routes, but I did find Tokushima to be a nice city. We hit four of the 88 temples from the Shikoku Pilgrammage, had some excellent ramen at a place called Toudai (apparently famous), hit a couple of bars and went to a club. Lovely folks, good food, and beautiful weather.
Kagawa was a little less eventful, but they're famous for their udon so we had to try that. I honestly couldn't tell the difference between regular udon and the udon we had in Kagawa, but wheat do I know? Beautiful scenery, though, especially going over the bridges that connect Shikoku to Honshu.