As others have said, I'm a big fan of Better Bottles for sour beer. Never had any excess acetic acid production, and I tend to be pretty sensitive to it. The risk of a glass carboy full of 18 month old sour beer breaking is too much for me (although I still have one that's been going for a few years).
My big issue with buckets isn't the permeability of the plastic, but the iffy-ness of the lids. Hard to be sure their seal is 100%. Similarly for any other fermentor, the biggest risk is not having a tight fitting airlock/bung. Or just as bad, an airlock that runs dry allowing the free-slow of air.