The "15" has less miles in a longer period... The "16" has a 4" lift that would concern me if they were Off Roading, or just a lifted grocery getter...
If I were looking, and I wanted a Ford F-350, and had those 2 to choose from, it would be a hard decision... I am not a fan of blue exterior, OR that color interior...
I like the silver exterior and black interior better, but those 100k miles is a bit high for a "16".. Not to mention the 4" lift..Im getting too old to drive any more lifted trucks
Your best option is to take a ride, kick the tires, drive them ALL, and decide at that point..