I asked a similar question last year and the replies I got were
overwhelmingly in favor of buying the percival chambers. In a head to
head comparison, no one could provide any advantage of the Conviron
chambers that would warrent their high price. I've since bought the
AR60L, AR32L and CU32L, and sitting in my hallway, they look great. Now
if i could only figure out how to get the univeristy to move them into
my lab and connect them ...