I'm using both right now... For my beers, I like the 6 gallon Better Bottle primary, and 5 gallon secondary. I have a "Chinese" knock-off that's going back... After just one brew going through it (in secondary fermentation, going to just 7% ABV) the plastic is showing discoloration (like it's been stressed) so I don't trust it at all. The Better Bottle (acutal) are not showing any of that...
If the weight of the glass isn't an issue for you, and you can make sure you don't drop them, or clink them together too hard, then you could go that route. In the small sizes the cost difference is typically minimal. It's when you get to the 5 gallon and above sizes that it gets to be a larger difference. Oh, and the plastic/Better Bottles have a wider mouth, so you can fit a larger funnel in there... Makes things easier on the pour I find.
I'm leaning towards long term, and high %ABV fermentations in glass... Short fermentations (a few weeks or so) and/or lower %ABV then the Better Bottles should be great... Of course, I would recommend staying clear of the clones since you cannot be sure they're built to the same standards (as I'm already finding out)...
I would also say, that if you do go both, make sure you inspect your carboys (both kinds) every time you use, or clean, them... At the first sign of something being not kosher, don't use them... You don't want to have it fail either in the middle of the night, or when you're at work, and come home to ~5 gallons of sticky stuff all over your floor (unless you're fermenting where there's a floor drain and hose hookup)...
), and wow! Much easier to move those suckers around, and especially to lift. You can even use two people if necessary. They also keep the carboys separated so they don't clink together disastrously.
