I was recently in your situation, couldn't decide what to replace the badly worn piece of Plexiglas that was on my cabinet that I am MAMEing with. Looked around and found Plexiglas available at Home Depot and Lowes, but it was all clear. Went to a local glass shop, they had grey tinted glass. I heard it was the best way to go. I had brought in my Plexiglas and they measured it and quoted me $18.00 plus tax for grey tint, cut and sanded, exact size. I figured what the heck, even if I didn't like it, $20 was not much to try it out. The Plexiglas I had looked at was all much more. I needed a piece that was a little less than 2' x 2'. The Plexiglas was available in 24" x 18" but then it went up to 24" x 48".
I picked up my glass the next day and took it home and installed it. WOW, it looked amazing. I did not have to adjust the monitor settings at all. I did not have to turn the brightness way up. I just left it alone and the colors really popped, plus with a black bezel that I cut out from black construction paper, everything is hidden. It looks like the monitor is just floating there.
I would go for the grey tinted glass. I think it looks amazing, is MORE scratch resistant and can be cleaned easier. Worse case scenario, you probably won't spend a lot and can try it and see for yourself.
Edited - meant to say more scratch resistant.