There would be the benefit of better brakes (in some cases) and some wheels only come in 5x100 now. The other difference is that the lugs are 14mm thick versus 12mm thick.

On your car its simple to switch to 5x100. Since you have rear discs already you would just get new 5x100 rotors. There are a couple of different ways to go in the front. You can get the necessary suspension parts at a junkyard. Or there is a company that makes a 5x100 hub that will work in your hub carrier. It comes as a kit with rotors calipers and hubs. That way you dont have to worry about changing everything.