There are various types of windshield glass. Some newer cars have acoustic glass or rain sensors built in. You need to be sure you get the right glass.
In general there are OEM glass and aftermarket glass windshields. Aftermarket glass is not required to meet the same federal regulations as OEM glass.
OEM glass is usually stronger and this may be important when you realize that the windshield becomes the backing plate for your air bags in a crash. The glass windshield provides up to 60% of the cage strength in the event of a rollover accident. The glass is not there just to keep the rain and bugs from hitting you in the face.
There are also things to be aware of when having a windshield replaced. Things like the age and type of adhesive used. The proper cure time before driving the car.
OEM glass is more expensive as it is more costly to make. Yet the windshield may save your life or your family's lives in a crash.
Here are a couple links to digest.
Frequently Asked Questions - OEM Glass, Windshield Replacement, Glass Replacement Phoenix, Auto Glass Phoenix
http://www.glass.net/auto-glass-info...uld-i-buy.html