I was looking pretty hard at the Osprey momentum for myself, but then I suddenly realized the back was just a molded hunk of something with no ventilation. They make awesome backpacks (I currently have two of their packs), and I'm really confused as to why they decided to make a backpack specifically for bicycle commuting that had no ventilation.

Anyhow, I ended up buying the Osprey Talon 22. It's geared towards mountain bike "bikepacking", but has been great for commuter use. But I recommend going to a local REI to see one in person. Depending on how much you carry, it might be a tight fit. For instance, I have a 13.3 inch laptop and I don't see it being able to handle much bigger than that.

No comparable input on the other bag, but I thought I'd weigh in on the Osprey.

EDIT: Felt I should add, the warmest weather I've seen with this pack is probably maybe 80, so I can't honestly vouch for something like 90 degree humid weather. I do get a sweaty back, but my back got sweaty without it as well, so I can't say it's any different. I plan on doing a "long term" report at the end of the semester.