Obviously it's not apples to apples because I'm running different tires, but given that I have both, here is my assessment.
HD3 is a very solid climber, with metrics tons of grip when running wide wheels. I pretty much just crank away with no issues until I run out of leg strength. You can more or less just doze off and easily cruise up fire roads in a happy gear. However, when you want to get on the gas and chase down your friend that just took off, you will remember that the HD3 is more on the all-mountain end of the trail bike spectrum, especially if you are running a chunky tires.
The Ripley on the other hand, encourages you though it's nature to fly up whatever climb you have in front of you. This bike makes me want to push it on the climbs and has a very different feeling under power than the HD3. Different != better or worse.
I have an Ikon 2.35 for the rear on my HD3 that is coming this week and I'll be riding both a lot in the coming weeks, so if you really want an near exact comparison on the exact same rear tire, I'll be happy to check back in.
Using the percentage meters, I actually think that the Ripley climbs 115% compared to the HD3 100% and to me, it's more about feeling and what it encourages me to do rather than actually being capable in one way or another.
I've taken my HD3 on days with 5k feet of climbing and it has done great. Would I have been faster on my Ripley on the climbs on that day? Probably.