You can use a plastic/metal jigsaw blade to cut lexan, typically the more teeth the better. However, Plexi is a horse of a different color. Plexi is best just scored and snapped. That or cut by melting.
Lexan is a bit softer, thus a bit more pliable. This makes it /seem/ more resiliant, and easier to use, but because of this, it is very easy to scratch.
Plexi on the other hand, is harder, so it breaks a lot easier, but is also more difficult to scratch.
Its a tradeoff... its always a tradeoff.