ABS is a lighter material, easier to produce for a Lower Price.

But ABS is also much more Flexible and it can be Prone to Cracking Prematurely.

FIBERGLASS is much more Stronger Material than plastic.

It does not crack easely and it is also way more stable under wind velocity as it does not flex.

 And the One Area where Fiberglass Undeniably Outclasses any PLASTIC/ABS product on the market. Is that it can be Easely Repaired. This Allows you to get the fairing and Keep it for the Life of the bike. 

 The possibility to have a removable fairing seems to be an attractive feature for many bikers. But the REAL FACT is when you Spend that kind of money for a Fairing you do not want your fairing to be Easely Stolen.  

A bolted fairing will not dissapear when you go to lunch for an hour. So you won't need to worry about loosing all that money if it get stolen. 

A Fiberglass fairing is a much better and stronger material for a Fairing. When install it becomes an integrated part of your bike.

Plastic is a Flexible material so Vibration or Flex under wind mouvement can be even felt when you ride. And with Removable Bracket System it can become really Unstable as well.