I prefer glass personally. I think they heat more evenly since they are thicker. Also, I like that I can see how the cake looks around the edges, to help tell when it is done or not and prevent it from getting burnt. Also, glass can take more of a beating when it comes to cleaning it. With metal, which is usually non-stick, I end up scraping too much of the coating off when scrubbing them, but also when I am cutting the cake in the pan as well.
With glass, usually if I just let them soak with some hot soapy water, almost everything just falls right off of them.
The only issue I've had with glass, is that sometimes it unexpectedly shatters. I know this can somewhat have to do with changing temperatures too quickly, but apparently it's also a common problem with Pyrex dishes these days too.