6 gallon glass carboys are preferred over plastic carboys and plastic buckets for a multitude of reasons. They are easy to sanitize and do not hold odors after fermentation because they do not scratch easily, so there are no areas to harbor bacteria. They do not break down over time and are airtight so if you handle them with care, they can provide decades of great performance.
Disclaimer - These carboys are made of glass and should be handled with extreme care. We have been able to use both hot and cold liquids in them, but they are not impervious to thermal shock and can shatter when exposed to large, sudden changes in temperature. Use caution.