The Pro 3 will have a better design and better display while the Pro 2 will have a slightly faster CPU but that also means lower battery life.
What do you plan to use it for?
I really want to try and use it do a little bit of everything it wont be the primary computer, but could possible be an everyday driver. I plan on streaming hd video, surf the web, do a little gaming when I cant be around my gaming desktop, run a couple of programs ex. photoshop