It's really not about double vs. triple. It's about cadence. You want a drivetrain that allows you to ride within your preferred cadence range at the speeds you are going to be riding. And, the speeds are a function of the courses (grades) and conditions (wind). I recently changed my drivetrain to a 34/50-13/29 for a 17.5 mile hillclimb TT and have decided to leave it on for my training rides. The reason is that I have more gear options for low speeds (e.g., <10mph) with this drivetrain and I don't mind getting into pretty high revs on downhills in my 50/13. I personally like to avoid changing my chainring (because I have to back off momentarily), so I prefer a double. But, it's really about finding a drivetrain that allows you to ride at your preferred cadences. Forget about what others are riding. You're riding against the clock. Bragging rights come with low times, not equipment.