Truckguy,
We have had the same setup as you and come around to the HDT conversion for the practical reasons that have been stated here. I feel like I have alot of experience on this subject so here goes......
You will never make an HTD conversion ride as good or as quiet as a bus conversion. You can make it ride very comfortable and quiet enough for most. Check out the pictures of my
unit on this site. You will see that we kept the sleeper and added a 30ft box. It serves us quite well. It does not turn as well as my first one or as well as the one Warpath built, but I am very comfortable in driving it as is my wife and we understand the turning limitations.
Check out how I re-did my exhaust.
Exhaust If you build a conversion and lower it then you may want to run yours the same way.
We pull a 32ft tri-axle trailer with 27,000+ lbs so mileage is not over 10mpg at the 75+mph I usually drive. I have a 470hp Series 60 12L engine with an autoshift. It does a very good job for me even though I do not think this autoshift shifts as well as my last one.
I think the difference in comfort for the family with an HTD conversion over the f250 with the 5er will be great.
If you do a conversion then you can always tow a vehicle behind you to use once you get where you are going.
You still have a ton of hands on research to do before you make a descion....
Good Luck
Wick