Microsoft expression web 2 and Microsoft expression web 3

I already have a free trial of Microsoft expression web 2 , but it has expired now so i am thinking of buy this software. I take a look on the Microsoft website, but i just find where they're selling the newest version, Microsoft expression web 3. So I don't know if there's many difference between the two and which I should buy it 2 or 3.
Any ideas ?
