Acrylic paint applied directly to canvas.
Glass is more carriage trade.
Plex is a little lighter and safer for sizes above roughly 16 x 20.
One misguided attempt to clean plex like it was glass will probably scratch the heck out of it.
Some galleries and many institutions are beginning to require plex for insurance purposes.
Glass it easy to cut but it wants to drink your blood. Cutting plex can lead to apoplexy unless you have a good wall mounted media cutter or table saw, but it is otherwise less lethal.
The lowest grade plex you should use is Acrylite-FF from you local plastic supplier like Piedmont. The stuff at Lowes and HD is crap.
Don't use window glass, use for-framing glass.
And there are probably another 50,000 words on this subject in previous forum posts.