Looking at 2 different power wagons...a 2010 and a 2013. The 2010 lists a 5 speed shiftable auto while the 2013 lists a 6 speed. I know that the 5 speed has 2 2nd gears so it could be listed as 6 but are there any owners out there that see a big difference between the 2010/11 and 2012+ years (performance, mileage, durabiltiy, towing etc)? Thanks!