You can always post links to prospective rigs and see what other members think. I always enjoy researching and examining older rigs and I often learn something in the process.
Another thing about older rigs is maintenance records. Higher milage and higher age make maintenance even more important and dealers rarely provide records.
Also many chasis/engine combinations had significant issues in various years and these are easily researched. Once identified you are equipped to determine if they have been addressed or ignored.
On the model hierarchy yes the MA is one notch above the DS and simce 2015 the MA has also benefitted from the ISX making an even greater distinction, although it is also around 4000 heavier.
Other distinctions include upgraded interiors and appliances, more standard items that are options on the DS and a little more effort on the exterior finish. But lookimg at 15+ year old rigs appliances are probably ready for replacement and exteriors will all need some attention, and many rigs will have been upgraded by now, so I’d ignore all that and look at condition, maintenance, and needed repairs. Tires alone will cost you $5000 or more so a rig with recent rubber is plus.
According to the 2005 brochures, the MA had a 400 hp vs DS 350 (ISM vs ISL?) and the 43’ MA had a tag - there were no 43’ DS models. So that may be worth the difference to you even if the “guides” don't reflect a difference in value. The quality of the interior of either will provide provide the same enjoyment level.
The DS higher reported resale values may also be a function of higher production numbers resulting in more sales from which to derive statistics. So for my money, unless you plan to sell ot soon, I‘d do a critical comparison of what you are getting for the price, and ignore NADA. A close look at RVT,com and RVTrader.com will probably provide more useful data.
