I know of no free site or service that will do what you want.
We have used the RV Consumer Group
when we were considering buying a new fifth wheel and again before we bought a new motor home. Their reviews are based almost exclusively on information provided by the manufacturers, but provide a good source for comparing brands. We found them very useful in ruling out specific brands and models of RVs. Take a look at the sample reports on their web site.
Everybody wants this kind of information for free, but I think it's worth spending $139 to avoid a $30,000 mistake.