Sam & Kim,
We just went through what you are about to go through. We had a 2008 Beaver Contessa 42. It was a beautiful coach with tons of room having 4 slides. King bed, over/under washer dryer, large screen TV, etc... So for my wife moving to a 99 Country Coach had its moments. Queen bed, dual function washer/dryer, much smaller kitchen, laminates, and far too many mirrors. However, the ride is awesome! Even compared to our 10 bag tag axle Beaver coach (not a bus conversion). Now we are getting ready for our first real trip (Tampa to Anchorage).
I would highly recommend spending some time with the service guru, Rick May, at Coach Worrx in Clearwater, FL. Even if you don't buy a bus there, you will leave knowing tons about the different conversion companies and options. Don't overlook eBay and RVT.com. There appear to be some good deals on eBay. We found ours on RVT.com. Tires and batteries are expensive! With discount, expect a set of Michelin tires to run you about $6K. Those 8D AGM house batteries are about $575 each and some buses have 8 of them! Bus air or over the road air have pros and cons. We have OTR air and dash air. Dash air is the same as any car in that cold air is delivered to the dash. Our OTR air uses a very similar engine compressor to that of the dash air with air vents in the middle and rear of the bus at floor level. Bus air has a huge engine driven compressor, air is typically discharged at the windows, and you lose a storage bay. Also keep in mind what refrigerant is used. I understand converting a bus air for the new refrigerant is a very expensive conversion. Cruise air or roof toop units... Cruise air split systems are common place in larger boats. There biggest advantage is they are quieter and don't require holes in your roof. There disadvantage is repair costs, loss of storage space, and refregerant conversion. The roof top units are now common place. They are relatively inexpensive and easy to change out. I too loved my Aqua Hot! I haven't turned on the Webasto unit but expect similar heating. For hot water I have 2 10 gallon electric hot water heaters.
When it comes to looks, I favor the riveted XL. BTW, late 90s XLIIs have independent front ends. Although it probably improves the ride, I've been told it was done to carry the extra weight.
This is what I've learned in the few monthes I was looking and based on what I purchased.