First question that comes to mind is how did the truck and 5er work for you last time?
We went back and forth on 5er vs C or A and we liked the idea of havjng a little house (the 5th wheel) to just setup and use like a little house. Since we already had a truck it made the decision even easier. In all honesty it's a no win debate. Everybody has their preference one set is better for x reasons and y setup is better for others. Shorter trailers are out there just not as common check out Arctic Fox (northwoodmfg.com) to start with. It's probably the most comparable to your old Hitchhiker in build quality unfortunately they don't seem to have a ton of dealers.
Re tow vehicles the two rigs you mentioned would be within spec for all current model 3500 or 350 diesel trucks. If MPG is a paramount concern look for a previous generation tow vehicles. My 05 dually with 5.9 gets 12+ mpg towing and 21 mpg highway unloaded. If going with the newer models look for the higher gear ratios to improve MPG and still be within tow rating. I wouldn't go back to gas if I were doing any real towing. BTW, i've only window shopped for new Rams, the prices you are finding seem pretty good to me just a lot more than what we paid 10 years ago...