Not necessarily better, just different. Here are the main differences.

    Glass carboys are:
  • PROS:
  • Impermeable to oxygen
  • Glass
  • Not plastic
  • Have performed admirably as the industry standard for decades
  • CONS
  • Heavy
  • Shatter when dropped (don't drop!)
    Better-Bottle fermentation carboys (PET) are:
  • PROS:
  • Unbreakable and tough
  • Taste- and Odor-free
  • Virtually impermeable to oxygen
  • Clear and colorless
  • Incredibly light weight, and more . . .
  • They are made from special, scientifically tested, polyethylene terephthalate (PET) copolymer plastic that is non-absorbing, non-porous, and non-wetting (hydrophobic), so it does not carry over flavors from one batch of wine or beer to the next and is easy to clean and sanitize.
  • Optional racking adapters and valves make oxygen-free racking and dispensing simple and convenient – no siphoning is necessary. Optional closures that use O-rings to make tighter seals are more easily cleaned and sanitized than conventional stoppers.
  • CONS:
  • Easily Scratched (no carboy brushes allowed!)
  • Will deform if cleaned with very Hot water (use warm water only!)

Don't even think of using common blue plastic water bottles, not only do they offer no protection of your beer or wine from oxygen during fermentation, they also are more prone to leach chemicals due to the solvent capabilities of the alcohol we just produced and that might  not be to good for your heath.

Carboys Made From Other Plastics –

Other types of plastics are not suitable for making fermentation carboys:

1) They are too permeable to oxygen,

2) They are not clear and colorless,

3) They scalp (release, pick up & transfer) flavors,

4) They stain,

5) They are porous and difficult to wash/sanitize,

6) Some are made with substances, such as bisphenol-A (BPS) and ortho-phthalate plasticizers, that are considered toxic