Some issues never go away - such as the navigation v marked course issue. In reality they are not comparable. A marked course means that everyone is tested against exactly the same course. It becomes a physical test - a pure race.
A fell race requiring navigation tests a different set of skills - though I don't think I have actually ever seen anyone navigating in a fell race.
A mountain marathon tests a different set of skills again.
Some formats definitely test a wider range of skills, though I'm not sue this makes them betteror more or less fun.