What's the difference between 3G phones and 4G phones?

I'm getting a phone soon and I don't know the difference between 3G and 4G. Which is best?What's the difference between 3G phones and 4G phones?
Honestly, there's not much difference.

Kind of like DVD and Blu Ray...



4G is just a little faster.
3G is a mix of circuit and packet switching network while 4G is only a packet switching network.What's the difference between 3G phones and 4G phones?
nothing unless you live in the 12 cities that have 4g.

4g wont be available everywhere until late 2012 early 2013
4G Phones are faster and have better coverage.What's the difference between 3G phones and 4G phones?
3g phones are slower then the 4 g phones
4G makes you feel bad for having 3G, so you want to buy it and the company gets more money.
Better coverage? better service possibly.
4G's faster