Dwight,
There is no definitive answer to your question. In fact there were a few years where the line between Magnum and Roadmaster was blurred because Monaco just changed the name on a Magnum chassis and called it a Roadmaster. As time progressed, the Roadmaster chassis improved and the Magnum plant in Harrisburg was closed as all Roadmaster chassis production for Oregon coaches was moved to Coburg. The improvements were mostly related to Federal laws that restricted or stopped the overloading issues that were very common on all diesel pushers in the late 90s and early 2000s. There was also technology advancements that provided better brakes, and the improvement in turning radius of later model coaches. However, there were several changes that Monaco made to Roadmaster chassis production that made them inferior to the old Magnum chassis, like the 4 air bag chassis under the Beaver Baron and Monaco Knight that had to be recalled because the arms for the rear suspension were so poorly designed that they were breaking off, and the side radiator fan motor mounts on high end coaches that were so weak that the fan motor broke loose and destroyed the fan and radiator.
To put it shortly, your friend is wrong. When comparing the same production year, there is virtually no difference between Roadmaster and Magnum, but as technology improved, the Roadmaster chassis improved and there was no Magnum chassis to compare it to.
Gerald
