Ran across this, thought it might be helpful.
Cast Acrylic has always been the better choice for routing, here's a couple reasons why:
Why use CAST Acrylic verses EXTRUDED Acrylic ?Continuous Service Temp: 180° F (Cast) vs. 160° F (Extruded)
Formability Temp: 340° F to 380° F (Cast) vs 290° F to 320° F (Extruded)
Cast acrylic has a higher molecular weight, therefore it will cut, drill and rout cleaner.
When machining cast acrylic, shavings will flake off whereas extruded acrylic shavings may gum up on the tool.
Cast acrylic also offers better glue-joint effectiveness and performs better in laser cutting.