What is the advantage of 4G SIM over 3G?

4g is about 20 gigs-ish plus what a 3g offers. Though 4g itself is actually not in existance. It's still in the making and it's looking as if it could take about 10 more years to completely have true 4g coverage. They refer to it as 4g but it really isn't. And the iphone4 isn't actually 4g coverage, it's just referred to AS an iphone 4, cause it's the fourth edition iphone.