All depends on how you drive.

The auto can not lug it down at lower RPM higher throttle angles like a skilled 6 speed driver if they have the same final drive ratio. Of course if you like to run around cruising at 3000 RPM @45 mph down the blvd then the auto will kill your 6 speeds mpg. The auto also has more frictional and pumping losses no matter how good the trans is

If someone wants to prove me wrong give me a truck with a 6 speed, follow me in the auto and I WILL get better mpg.

Almost forgot, I think the autos may be using MDS (can't think of any reason not to put it on the manual trans except to make the auto look better so you spend more money)if that is the case it could help sway it to the autos favor but I still think I would have a real chance in town. If they both have MDS the manual with a skilled driver still wins.