My original Boxster had a plastic window. When I replaced the top, I got the slightly smaller glass window. Didn't make much difference - view directly out the rear is fine but the 3/4 view is blocked by the top with both types of window.
I never did the chop with my plastic window and never had any problems but it is relatively warm here in LA most of the time.
What made a difference to me was clarity; if the plastic window is yellow, clouded, or scratched, you will appreciate a clear window when you get one.
