Opinions are often very subjective and can't make accurate assessments, especially in matters like this where the two things being compared are vey much alike. The only objective way of doing it is to have accurate temperature and humidity readings over a period of several years for both places. Someone has probably already done that, but I don't know where the best place would be to see their results. Being a relatively small island, Guam should have a marine climate, which is less extreme than continental climates. We have a marine climate here in Britain, and though we often complain about the weather it is less extreme than weather in Europe. A marine climate gives us cooler summers and milder winters, as the temperature is moderated by the sea, which also gives us a damp climate. Guam is nearer the equator than Maryland and is rainforest country, so I would expect it to be fairly humid but not so extreme and variable as Maryland.