Plexiglas is technically the correct spelling, as it's a brand name.
Plexiglas advantages: cheaper, a little sturdier (and flexible).
Disadvantages: as previously described in the thread (scratches easily, static cling).
Glass advantages: much more scratch-resistant, easier to keep clean.
Disadvantages: heavy, breakable, more expensive.
There's also acryclic, which some people use for enclosures. More scratch-resistant than Plexiglas, but I think it costs quite a bit.
As far as the difference in thickness, it's not like the collareds are gonna "bust through" 1/8" material. However, it IS something to consider if going with glass--the thinner material will be easier to break through unfortunate accidents etc.
-----
Chris McMartin
www.mcmartinville.com
I'm Not a Herpetologist, but I Play One on the Internet