I have one large plastic wine carboy but the plastic is only translucent, not transparent, which I don't like at all. I believe the Better Bottles are clear. I've been using glass for the most part, it's heavy though and if you aren't careful you can get hurt if you break one. I do use plastic 1-gal water bottles for fermenting when I run out of glass jugs and I haven't had any problem with them. although I did end up getting bigger stoppers to fit them. A good wash (or soak, if it's really bad) with the pink cleanser takes any residual flavours right out.
Regarding stopper size, I ended up getting an assortment of stoppers in sizes from 6 to 9 because every make of glass carboy was slightly different, of my 8 or 10 three-gallon carboys I think most take 6 or 6-1/2 and a few take 7, of my 5 gal carboys, most take 7 and a few take 7-1/2 or 8 and one takes 6, all my 1-gal glass jugs take 6, my primary fermenters are mostly 7 with one or two larger ones, and I got a couple 9's for the plastic water jugs. The plastic carboy takes an 8... but at least stoppers are pretty cheap at $2 each.
The one con I have found using plastic is that they aren't rigid enough, so that when you pick them up and move them around, the bottom tends to bow out and they suck in a lot of air through the airlock, and if you're trying to avoid oxidation in an aging wine, it's not ideal.