Carboy:
Pro's - you can see inside of it.
Con's - harder to move around, need to cover it, PITA to clean
Bucket:
Pro's - easy to clean, no threat of light exposure.
Con's - Top can blow off, cannot see inside.
I use both. If I know it's going to be a long ferment I use the glass so I can monitor. If I know it's going to be a blow-off threat, I also use glass. Otherwise I use my buckets.