There's usually very little difference between carriers, and for every good thing somebody can tell you about one, another person can tell you a bad thing about the same one.
I will say this, though... I met two Air Canada pilots in Manchester last year. They were doing the flight from Toronto (I think) to Manchester, and had a night off in the city. Nice guys, very strange night. Me, an American, two Australian professors I met at a conference, and the two Canadian pilots. People peeled off through the night until it was me, the female professor, and one pilot, wandering around town after last call, looking for toilets and a strip club.