I had a pair of Bose QCs... they were my second pair of phones after SR60s (bought years earlier and shelved for being too bright and I found them uncomfortable). When I first heard the bass in the Boses I was blown away, so I bought a pair for £200. After a year they fell to bits because they're seriously fragile. Then I tried the Grados again, and discovered I hadn't used them enough to let them burn in. I back-to-backed them with what was left of the Boses and the Grados were way ahead on detail, soundstage, and all frequencies except mid-bass - but the Boses just sounded like someone had already EQ'd them at the factory, so I was getting a pre-coloured sound. Which was okay on its own, but felt artificial after the Grados.
Inspired by this forum, I bought some Shure SRH750DJs - because I like me bass - and they are another step up again from the Boses and make them sound flat, muddy, one-dimensional. Then I bought some Sony XB700s (more bass) and they're better, in a different way (waaay down low), again. And they I bought some AT AD900s, and although they're bass-light in terms of quantity - plenty of extension tho - (unless you turn them up VERY loud, which is killing my hearing) the detail, purity and clarity of the sound is a rapturous eargasm, every time.
So, for me, ees simple. Bose is a lot of money for not much in return. Poor build quality, poor sound quality. If anyone asked my advice, I would say only buy them if you're too lazy to find better and have never heard better. Or if you're trapped in an airport and it's all they've got and you've got more money than patience. It's not about being a headphone snob - who cares enough about that? - it's just if your ears can't hear the difference, just buy the cheapest you can find; if they can hear the difference, then why spend more?