To like or dislike stacks is purely subjective as stated above. How you install them and how your truck is setup to appear make a tremendous difference in if they "fit" the look o the truck or not. How your truck is modified and single or dual stacks will also make a huge difference in the sound produced.
I run dual 5" flat top stacks off a 5" T-pipe I built myself. Under the truck I run a 3.5" down pipe into the cat and 4" to the T-pipe for now. I also have a cat delete pipe if I choose to make some noise.
Granted, I'm not running a 6.4, and there will be some distinct sound differences due to the injection system and turbo differences, 6.0s can be obnoxiously loud straight piped and tuned. I find that with my truck running stock or mild tuning, straight piped it sounds like a healthy big block from days long gone.
I tow with my stacks too. I have an 11,000 pound 30 foot 5th wheel. Last year we drove all the way from SoCal to Minot ND, then to SD, WY, MT, ID, WA, OR, and finally back home. Almost 7k on that trip alone and over 10k in travel last year total. Noise is not an issue in the cab. Soot is a minor issue that is easily remedied with soap and water and a car wash brush on both the truck and the trailer.
Here's my final thoughts. I wouldn't do a 7" stack on a short bed. You don't have much bed left afterwards, a long bed is another deal completely. Also, go at least cab height or just slightly higher to avoid sooting up the back of the cab and the bed.
It's your truck, do with it what makes YOU happy. That's why I did mine.
