I am not sure I have enough knowledge to answer the questions about the climbing geometry, but I would assume the Sirrus has a bit more aggressive geometry so it might be better. Stiffness might make more difference. I did have a vintage road bike that I remember flexed alot so it probably wasn't a very good climber. Of course I was at least 35 pounds heavier then so maybe it wouldn't flex as much now. =) It certainly doesn't flex much as a frame sitting in my basement.

As a commuter I rarely think about climbing because my hills typically are the last mile of my short commute and so I don't usually push myself much. I have taken to spinning up hills. I don't know how much climbing matters to you. I would think climbing hills is more about the rider than the bike. Also I am not sure how well anything climbs when you have it loaded down with a few extra pounds of accessories and whatever else you might be carrying. I weighed my commuter today and it was around 40 pounds.