For those who are concerned about possible injuries to gallery patrons and employees from broken glass in frames, here is a solution that is quite inexpensive compared to shatter resistant glass made for framing. 3M or other brands of add on security film. Convincing competitions that forbid glass in frames that this is a viable option is another hurdle, but you can at least use this film to reduce your own liability if you prefer glass over plastic glazing for whatever reasons.
Pick your favorite glass then apply the security film to the inside. The cost savings when using regular inexpensive glass vs high quality plastic glazing is substantial. I have not used any but plan do do some testing with leftovers from an upcoming DIY home window installation, and will report back.