Get the 8 speed, you will like it far better. If you don't need the ability to tow 10,000lbs get 3.21 gears. I had a 2013 with an 8 speed and 3.92's and it was still hard on fuel on the highway. I just traded it in for a 2014 with 3.21's and it revs 4-500 rpm less on the highway.
On the highway today it got 20mpg compared to my '13 that got 17.5. Remember my 2014 only has 600kms so it's nowhere near broken in.