When I was deciding whether to keep the 9s or the 10s, it wasn't as easy a decision as I thought it might be. The 10s are technically the "better" headphone, but my version of the 9s (again, I've heard another with a different sound) had a wonderful, slightly gentler sq, which I really enjoyed. I already own headphones that offer me that (Senns, R10s), so I chose the 10s, but I could have been happy with the 9s without a doubt.