Given the age and the mileage on both, that means they sat still a lot. Sitting and not running can be as damaging to equipment as running a lot. You would be wise to get a thorough inspection done to make sure the proper maintenance was performed to keep not only the engine, but all the equipment in the coach running.
You didn't mention tires. Again, if they haven't been changed recently, you are looking at new rubber all the way around. Look up some of the tire discussions on this forum.
Does the coach with the water stains have a rubber roof or a fiberglass roof? That vintage most likely has a rubber roof. Depending on how they were stored and maintained, you could be looking at a new roof. Just the material for the roof is around $800. And, there is a significant amount of labor involved. At minimum, you want to get on a ladder and inspect the roof.
Stains on the ceiling do indicate water damage. My original ceiling showed just a couple of stains, but the water damage was significant when I started taking things apart. An inspection might turn up some of that.
As to the engine power - I have no experience with the smaller Cummins. My Cummins is the 330 with a turbo-charger and it has plenty of power on my 40'. Maybe someone else can chime in on the Cummins 5.2L.
Both coaches are well known brand names and parts should be readily available. Just keep in mind, you are buying a house on wheels. It's a little different than shopping for a car.
Best of luck. Hope we see you on the road soon.
Al & Sue w/T-Bone & Rosco
Go Devils Bus, 1994 8.3 Cummins, Spartan Chassis