I've had a 2011 F250, with plenty of engine, but not enough suspension. Bought a 2014 F350 DRW that pulls so much better I was shocked. To answer your question as far as 2013 it will be an excellent truck as long as you get one setup for your potential load. The 6.7 Ford engine is excellent. I've had zero problems between the 2 trucks. As far as the 2015 I'm not sure if there is any advantage. Maybe a little more HP. I do not see the need for anymore HP.