Hi Norric. Cannot truly say "I know", but I can say that the surface area of a bucket is large and after the yeast quit producing CO2 that area and the volume above it is likely to be filled with air and that means that you can expect to very greatly reduce the shelf life of your wine because of oxidation.
One reason that carboys are used is because when filled up to the neck the surface area exposed to air and the volume of air that can sit on the wine is very small. In other words, I would argue that buckets are perfect for active fermentation. They are not good as a secondary, and are beyond a last resort for use for aging.