I have a compact double on my road bike (50/34, 12-25) and really easy gearing on my MTB (42/34/24, 11-32) and find that climbing is very different on both. My road bike is 18 lbs, fully loaded, whereas my MTB is much heavier since it is not only a heavier bike but also often loaded down with work stuff, etc. But I can take that bike up hills I'd never manage on my road bike.

For me, I prefer the road bike for non-steep, sustained hills (below, say, 8%) and for short, steep climbs. The former just melt away on the road bike and the latter are more painful than on the MTB but they are over really quickly.

The hills that I still really have a hard time with on the road bike are *really* steep hills (i.e., the 18% grade on one of my commute options) and steep, sustained climbs. I have to walk up the former and stop occasionally on the latter, whereas on the MTB I can shift down, spin along a little then shift back up when I am refreshed. On the road bike I have to grind on up the hill, and maintaining a workable cadence really pushes the limits of my fitness; I have to stop every few miles to get my heart rate down. I definitely feel that the compact double is great for climbing, but I am having to increase my fitness to get up some of the hills that seemed a lot easier on the MTB.

For what it's worth, I personally feel that the weight issue is a little overstated. I notice little difference in the ease of a climb, for example, when I have 10+lbs more or less on my back. Tire size, pressure, bike stiffness shocks/no shocks, riding position...these all make a difference and for me at least it is difficult to separate them.

I do a decent amount of climbing and have been really happy with a compact double, hopefully you'll have the same experience. And congrats on the new bike!!!

Anne