I'm getting OC and the wiper marks on my windshield are really annoying me hehehe. I tried to have them polished at Big Bert's and it got minimized a bit but it's still not as clear as I want it to be. I got a quote from Aguila Glass for 4k for a replacement windshield.

My questions are:

1) What exactly is the difference between the original windshield and a replacement from Aguila?

2) What about surplus windshields? Are they ok to buy? How's the condition of these, usually? Still ok or they're scratched up as well?