I was using a big carboy, it must be 8 gallons, until I decided I'm not going to mess with glass anymore. Just switched to an 8-gallon bucket (two, really). Always used a 1" blowoff with my carboys, only needed it once . . . but that's why I used it every time.
I've never used a glass fermenter, but I don't see any evidence that the Better Bottles would be less sanitary than any other solution. They're certainly much less likely to sever any limbs if I slip while carrying one around the house.
The only annoying feature is that they tend to suck back on their airlock when you lift them, since they're a bit flexible. No big deal, though, I just pull the airlock when I have to move them.
To keep this on topic.. I have a 6 gallon BB for primaries and a couple 5 gallon BBs for secondary. I usually do about 5.3-5.5 gallon batches, and I frequently have fairly significant blow-off even with the 0.5-0.7 gallons of headspace.
I am using 6.5 gal better bottles now. I have two going at the moment. I was using the 6.5 gallon plastic bucket, but I hate racking directly to kegs with it. I always seem to get some trub into the keg. With the ported better bottles and the racking valve, I get clean beer without having to secondary or rack to another bottling bucket.