I love my 2016, and my wife's 2012 isn't bad either. I'd skip ahead to 2019 if you don't want a 2016. The 2015, 2017, and 2018s all had a lot of 'teething' issues. The 2016 is great as long as you get all of the TSB updates done. The 2012 -- 2014 are also good. The 2015 and 2017 were the first major change years, so I would avoid those if possible. If you want the older hydraulic 4WD, you can go with the 2011 or on down. It all depends on what you want.
Always get the maintenance information if you can. If you can, look at the Maintenance Minder to see if anything is about to be due, due, or overdue. I noticed on my CarFax report that the dealerships only listed 'vehicle serviced', but didn't go into everything done -- but the MM was clean... I still had my new service dealer do all of the fluids just in case (32,000mi), but everything felt good when I drove it off the lot -- no differential noises or any other abnormal sounds. My new service dealer said everything looked good during the multi-point inspection, but went ahead and did all of the fluids for peace of mind and to have it officially documented and sent to CarFax in case I wanted to sell the truck later on.