it depends on the era. Back in the '70s, I wasn't that impressed with Dura Ace mostly because Shimano was famous for not being able to produce spare parts when needed. I always thought that Campagnolo Record was only a little bit more expensive but a better value. The next step down from Dura Ace/Record was a fairly big step in fit and finish and durability. Suntour rear derailleurs worked better, but they were not top of the line and really were out of place on a high-end bicycle. It's apparent nowadays that the difference in function with the lower levels of components is fairly small.