The different gears in the 6 speed are due to the tire diameter. As far as the acceleration between the two, it will be almost identical. I have ran 3.91, 4.10, and 4.30 gears in my race car. The only thing that changes is the trap speed (slightly) and the RPM's. The ET is virtually the same.

Lastly... I would not pay any attention to the road tests you read in magazines. There are many people that are getting better times out of their stock cars than the rags. You best bet is to test drive one of each.