I have a 10 gallon bucket that is currently only used to store equipment, though I'll probably end up fermenting in it again if I run out of carboys. As has been previously stated, it's mainly a matter of personal preference, though there are pros and cons inherent to each one. Here's how I see it (I like lists):
Carboys
-Pros
-->Clarity, you can see your beer without opening fermenter
-->Less headspace for reduced oxygen exposure, ideal for prolonged aging
-->Smooth, hard surface doesn't harbour bacteria
-->Not oxygen permeable
-->If properly cared for, can outlive their owner
-Cons
-->Heavy
-->Fragile
-->Harder to clean
-->More expensive
-->Harder to store when not in use
Buckets
-Pros
-->Lightweight
-->Impact resistant
-->Easier access for cleaning
-->Usually much cheaper
-->Stackable for storing
-Cons
-->Can't see your beer without opening fermenter (except maybe PC buckets)
-->More headspace, not ideal for prolonged aging
-->Surface easily scratched, may increase infection risk
-->Many plastics are oxygen permeable
-->Tend to wear out over (a long) time
Again, it comes down to what your priorities are. Buckets do have a pretty solid edge when it comes to handling/cleaning, whereas carboys are the better choice for bulk aging and potential lifespan (you could use the same one for hundreds of years if you don't break it first).
You decide based on your own needs and don't listen to anyone who tells you that one or the other is the wrong choice for you.