Acrylic is not completey smooth like glass. It has microscopic size divots and craters which over time can harbor microbes and cause the acrylic to cloud or stain. This is more of a problem in the world of aquaria and fishkeeping due to green algae, but I would imagine snake urine would stain/cloud the acrylic too.

Another thing to think about would be heat conduction and retention of glass vs. acrylic for a UTH or flexwatt. Anyone want to chime in with which one is better regarding this aspect?

edit: check this out http://www.firsttankguide.net/tanktype.php

Again, mainly for fish keeping/aquaria, but still has good info.