it will be acrylic.
plexiglass is acrylic and as far plastics go, it has a high scratch resistance, and will withstand a moderatly high impact when new, but the impact resistance goes down over time
lexan is polycarbonate, which has a very low scratch resistance, and can be scratched/permanently smudged simply by wiping it too hard with a dry towel (or even by rubbing your finger on the surface), but it has an extremely high impact resistance (1/2" and thicker are bullet-proof) and will remain so for many years....
but the good news is, both materials can be purchased with an armor coating on the surface that makes them even more scratch resistant.... the bad news is that the coating can wear off before the life of the plastic fades....
acrylic is a bit cheaper than polycarbonate, but the armor coating on either, adds significantly to the price.
I would always choose the acrylic over the polycarbonate, unless, 1... I was expecting someone to be shooting at me.. or 2.... it had to be very thin material and I expected it to take some very sharp blows against it... because it scratches and hazes over so easily.
the acrylic in 3/8" and up can take some good impact without damage, and when you get into the 7/16" and 1/2" thicknesses, you are beginning to equal the fiberglass you are bolting it to... 1/2" and thicker acrylic is commonly used to create frameless windows, that bolt to the cabin trunk on bluewater cruisers.
polycarbonate is a good product and is shied away from ONLY because of its so easy to smudge/scratch....and the cost of the armor coating that can wear off over time, or be etched away with some common acids.
. should be available at most glass shops, and comes in a 4x8 sheet that they can cut down to whatever size you need. enough to replace all four of my windows (Mac 25) was about $80.00
