For me, mtb's are easy, if they are hand made, steel and from the UK, then I'm happy.
Road bikes are a lot more difficult, as there are some excellent factory steel bikes, and some right clunkers, then there are the hand built bikes, but with so many makers through the years, who's hot and who's not, or who sold bikes under one name that were made by someone else (rather like many mtb's; UK company, frames made ....abroad).... and on and on, with fine names being bought up and then used as a brand for lesser models of the bigger manufacturers, Carlton, Falcon, etc, even Claude Butler. It is a real minefield for the unwary.
Of course, the fact that mtbs have only really been about since the late 1980's makes life easier, where as fine road frames have been around several decades longer.
"Try not to punch any clowns"