Finding a new pickup can be hard, frustrating and fun! You need to find your preference and act on it. The biggest thing is don't settle for something just because they have something on a lot for a good price! I have some info to hopefully help you. I am a very big diesel enthusiast and have rebuilt multiple motors and do all my own repairs.
Well Ill tell you that the 6.4 your current pickup has is one of the worst ford made, it saddens me to say that because I am a ford man. The new 6.7L that for has are bulletproof, I have a lot of friends who are ford diesel mechanics and they will stand behind that motor all day. The 7.3L which was in the 99.5-2002 Ford was one of if not the best motor that ford ever had but due to emission testing the 7.3L was able to meet the standards. The motor after the 7.3L was the 6.0 and Im gonna tell you not to even look at the 03-04 because they are a nightmare but in 05-07 they fixed most of the major problems that were happening with that 6.0 I currently own a 2006 F350 with the 6.0 and I love it but I do take great pride in the maintenance in it. I feel that the cabs of the fords are a lot more roomier and a little more "comfier or cozy" feeling but that is just me.
As for Dodge, they have great motors, the 5.9L which was in the years 2003-2007 was a great motor but the biggest downfall about dodges in those years that had that motor were the transmissions. The auto trans were just plain junk and that is why you will see most of them that are for sale to have had the transmission replaced and a majority of the ones for sale are automatics but you will be able to find a manual, so i advise you to stay away from the automatics! The 5.9L was very low cost in maintenance and that is always a plus and most of the time parts for it were not a whole lot such as filters and such. In the years of 2003-2007 the dodge made a 4-door option but the backseat was actually the size of an extended cab of the other truck makers, but they do offer the mega cab which is flat out awesome in the backseat! My friend who has a megacab shortbox dually gave me a ride once, and I loved it and it has had an amazing turning radius which was vey surprising. I am not real familiar with the 6.7L engines that dodge now has but I have not heard any horror stories from anyone so far, so that is a plus!
Chevy has a great combo with the Duramax diesel and the Allison Automatic transmission. I worked for and with a guy who bought nothing buy Duramax pickups. Now the 6.6L is a reliable and powerful engine but it is also known to be kinda prices to maintain if you want to keep it running, not saying that you won't be spending money on any of the previous pickups but I've just been told its pricey. I know that the injectors in the 6.6L have been known to go out, and as with any injector you will have to spend what seems to be your retirement savings. Having the reliability and confidence of the Allison transmission while towing is awesome and it pulls just like a manual transmission but its great not having to shift! The Chevy seats are extremely comfy and pry the most comfortable of the all the pickups but I have not sat in the new dodges or fords. Im not sure wether or not the seating or cab features make that big of deal to you, but its just something people really enjoy.
Now I must tell you, if you are going to buy a pickup from 2011-and up you will have to use a product that is called exhaust fuel. The point of having to use this exhaust fuel is that its suppose to "come out cleaner than when it went in". Now I have a friend with a 2011 dodge diesel and he does not have to use it, I'm not sure if thats with Dodge or just the pickup he bought.
Someone earlier said it perfect, its all about person preference and you really should do A LOT of research before you buy. Knowing your stuff about the pickup will help you be able to find the things that may need fixed after you purchase it and knowing your vehicle is a great thing to have behind you anyway! There are tons of forums just like this but for each pickup so look on there for anything and those people on the sites know almost EVERYTHING!
Sorry I wrote a book buy I really wanted to help you out and let you know about the many options out there for pickups and also give you some background information to build your search off of!
Good Luck!
