To the sound, I can say the following: I think the Bose QC 15 perfect for my ears. I like the typical sounds of the Bose sound balanced and clear and it shows the bass, which but not exaggerated as eg when the Monster Beats. Even at full volume music in rock and trance-sector is still a pleasure.
I have previously also products such as Sennheiser tested (PX210BT, CX880i) have not impressed me by the sound and also expensive, monsters - but> cruel thoroughly, B & W P5 good as the Bose because I lacked that certain Something. Devil Aureole Fidelity Titan were at best but the bass was barely there and there IN EARS also not perfect.
Battery life is very good. I hear regularly music & audio books and get along well with 1-2 weeks of battery.
Comfort as mentioned much better than the 3 Series for my taste. The tested competitors could not keep up rudimentary since.