I don't usually comment but I just broke my first carboy a couple weeks ago, so relevant. Five gallons of pumpkin gingerbread ale splooged all over the garage floor. I was heartbroken, to say the least. Almost busted a kneecap, and had a big black bruise to show for it, but fortunately kept all digits and broke no bones. That said, I still prefer glass over plastic and picked up a new 5 gal carboy today to store my cider long term.
For the typical 5 gallon batch I use:
-6 gal glass carboy for primary for added headspace
-5 gal glass carboy for secondary and long term aging, or
-cornie for long term aging
I'll only use plastic buckets if all my other fermenters are in use, or if I'm using a ton of whole hops which might plug the bunghole or create cleaning problems. I'm not concerned so much about scratches harboring bacteria and I've never had an infection from my buckets, which have been in use for many years; a proper and rigorous cleaning and sanitation regime should take care it. Rather, I'm concerned some of the plastic compounds might leach into the beer over time. It wasn't until recently that they finally banned BPA in plastic drinking bottles, after all. Granted, city living likely exposes our bodies to far worse, but the beer must be protected at all costs. ;-)