I use a compact double 50/34 with various cassettes. I used to have a 52/39/30 Shimano triple which was nice and worked great. And I have a 53/39/30 triple on the tandem.
On the top end, a 50/11 is a big gear and generally all that I need even to do low cadence intervals on flat to rolling terrain and the 50/11 is bigger than a 53/12. The first cycling coach I used (I am back with him this year) wanted me on a 50/34 primarily since I am a trackie. He wants me spinning faster.
On the low end, 34/XX just offers a lower gear than the 39 by a few percentage points. For me, it is not about whether I get up the climb but is my cadence optimized for the effort since I can always stand and climb using a bigger gear.
Being competitive is another matter. In road races or fast group rides, climbing speeds are faster and many times I am in the big ring so low gears are useless or one is off the back.
When I climbed Mount Ventoux, my lowest gear was 34/30 and for the 4 miles of 10% grade, I could have used a lower gear just to spin a little faster and take some of the pressure off my legs. I do not think it would have changed my climb time or VAM.
Eventually, I will change to the 11 speed technology and that will provide me with all the gears I need with a couple of cassettes.
IMO, having low gears offers no downside and one can always increase the cadence and keep the climbing speed the same.
Last edited by Hermes; 05-05-14 at 08:41 PM.