Greg1,
Here is a way to compare both coaches manufactured by Monaco. Click on either Monaco or Holiday Rambler, then go to to "brochures" at the top menu. I clicked on 05 Navigator for the HR line and 05 Dynasty for the Monaco line. Both have the RoadmasterS Chassis. Engine is different as I am sure are some of the options but you can get an idea of anything significant. I don't think there is but Monaco seemed to offer a few more choices in the motorhomes for that year. I know the Dynasty, the Signature and the Executive were their higher end coaches in 05. You will also see how the roof is put together and you can branch out to other links about their chassis, etc. There are some differences but both had the ceiling height increase in 05 and some other perceived upgrades.
http://www.monacorv.com