I've stated it before, and I'll state it again... I don't like buckets for fermenting beer in... Period... They're ok for fermenting a melomel if you're adding fruit in at the start. Otherwise, I don't use them. Period...
As for what you ferment in, completely up to you... I will advise against racking a brew before it's time to bottle/keg it from the yeast. I'm going 3-6 weeks on the yeast and getting GREAT brews time and again.
While I do like to see the action inside the carboy (either PET or glass), I'm slowly making the shift over to SS for fermenting and aging... I have my first brew that started in a 5 gallon corny still going (started on 2/26) and only used an airlock in it (we used fermcap in the boil, didn't need a blowoff tube at all)... I'm in the process of cleaning out four 5.16 gallon Sanke kegs that I'll be using for fermenting and aging brews in... I'll probably still use the carboy's for brews, until I have more kegs to use... I will be getting some corny kegs to age my mead inside of soon... That way, I can tuck them away for another ~6 months before bottling them...
Of all the choices, I see stainless steel as the best for fermenting/aging in... Smaller footprint than either carboys or buckets, and you won't get any light/air penetration. Pretty hard to beat that. Plus, if you happen to drop one, and fall on it, the worst thing that will happen is your voice might go up a notch.

Well, unless it falls on YOU that is, and is full of brew...

Zero chance of it shattering and you getting stabbed.