I haven't had a chance to do an adequate test in both modes. Bike onloy has a few hundred miles on it, but so far I'm getting 40.8 average. That's a mix of both Sport and Touring and both highway and backroad. Maybe this weekend I'll try a comparrison test.
I tend to use Touring mode for the commute to the office and for two up riding (it's a little smoother) and Sport mode for everything else. I could see myself just using Sport all the time though. I just play with Touring mode because it's there.