From my perspective as an amateur racer who competed locally in both DS and 4X back in the day, I enjoyed DS more. DS was more about rider skill and fitness than 4x - which is more about balls, aggressiveness and luck. 4X is more spectator and TV friendly i guess, and probably doesn't take as long to get to the finals. Wisp, MD was always my favorite track but Plattekill and Blue Mtn had some good ones too depending on the build. Most memorable DS track though was on Campus at UMASS right next to a dorm (XC course was there too). Collegiate racing was a blast. Aaaand now back to your pro racing talk...