Nearly everyone has an opinion on this subject. I do too.
Since 1960 I have purchased five RVs, all new. I have never had any problem during the warranty period that was not taken care of by the dealer at no cost to me. In fact I have never had any really serious problem at all with any of the five.
Although I have never purchased a used RV, I have sometimes talked with others who have "purchased other's problems" buying a use one.
Concerning the comments about depreciation: Since the 1970's we have used each of our RVs for a number of years before trading up to the newer model. Due to the fact that I always keep our RV in excellent condition, and due to the massive government policy inflation we have experienced over the past 40 years, I have always been able to receive close to, or even over, the original price that I paid when I trade in the used one. Measured in Dollars, I have never suffered any depreciation on the older RV when I sold it to the dealer when replacing it with a new one. Naturally, if I had traded within a year or two I am sure that there would have been some depreciation.