You can still see in a better bottle.
Glass is tradition and people like it better just like you would like to drink out of a glass instead of a cup. The only real advantage for glass is that it's harder to scratch. However, it's so easy to break compared to the better bottle, and the plastic is so easy to handle when cleaning or moving wort I would never consider glass. Wet glass is so slick i wouldn't want to have to clean or empty a full carboy.
A lot of people siphon cleaner out of their carboy, while I have no worries about just tipping it over and pouring it into the sink with the better bottle.
One random tidpit, I heard theyre going to stop making glass carboys? Some manufacturer in mexico shut down does anyone know if that's true?