As others have said, no one's personal opinion is going to be right or wrong on this debate. When I looked at a new coach I considered the following:
1) What's my intended use for the coach? Shorter local travel vs. long haul, how many miles per year. This will influence your operating costs. The more you drive, the more the diesel makes sense.
2) Budget? You get a lot more for less with a gas coach than a diesel. There is a LOT more involved than just the engine. In fact, I think the biggest difference is the chassis/suspension design, with diesels being built for better long haul comfort/durability with air suspension, etc. This is the primary cost driver, not the engines. A ISB/C diesel engine is only about $5,000 more expensive to produce than a gas big block, but the chassis' that hold them are $40-50k more expensive than a high-rail Ford or Workhorse gas chassis.
3) Investment horizon? Are you keeping this coach "forever"? If so, diesel starts to make more sense. If you are going to resell in less than 10 years, the benefits begin to taper off on resale.
4) Maintenance? Who is going to do it? If you are like me and prefer to do a lot of your own maintenance, a gas chassis is basically a big car and about as cheap to maintain. A diesel may require specialized expertise, tools, and equipment depending on the engine/chassis.
5) Personal preferences? Whadya like? Always the wild card with any purchase. No logic can overcome the hearts desires (or the checkbook's limitations).
So, at the end of the day, if the question was really just "gas or diesel" then diesel makes the most sense in heavy over the road vehicles, no question. The issue is that gas v. diesel is rarely if ever limited to the engine choice.
BTW, I have a gas Ford F-53 chassis, and I have no issues with the engine at all. All the power/torque I need and OK fuel economy. The suspension on the other hand, is not great and I've had to make upgrades to improve performance.