Any front windshield glass is going to be a composite glass with a sandwhich of plastic in between glass panels. Depending on the type of glass and the manufacture determines how thick the plastic is going to be. The front glass is made to deform but not break under stress from an impact to help protect the front occupants. We have special saws in our crash kits to help us cut open windshield glass during extrications. Besides the saws, we can also use a flat-head axe to help cut away the windshield glass in order to do a roof-away extrication. Windshield glass is extremely durable and very tough to punch through unless you have an RPG.
Side glass is different. Side glass is typically tempered glass which is designed to shatter on impact. Tempered glass is made to shatter into extremley small pieces in order to not "dice up" the occupants. Temepred glass will go everywhere on impact but typically do very little traumatic damage to it's occupants. If we were to try and make entry through tempered glass, we would covert he glass in duct tape before "opening" it in order to help more protect the occupants from flying debris.
Automotive glass nowadays is very high tech and in the coming years is going to become more and more difficult to penetrate..
