I personally have the Sony MDR1000 but that's cause I got it for a really cheap price.
On that note, I'm not saying it's bad. I love it, it's my first noise cancelling headphones.
I've also tried the QC35, the bose is definitely more comfortable but looks wise they're both ok to me.
I'm not an audiophile of any kind, for me the mdr1000 sounds great and the battery is amazing as well.
I heard the PXC 550 can get sweaty around the earl. It's also a design that's not for everyone. You can't go wrong in terms of noise cancelling tho, but I heard (again not an audiophile) that sennheiser is best when it comes to sound quality.