You will most likely notice that the size isn't all that different.
I have a Blackbook, and most of my friends have a MBP. The size difference is dramatic, and that picture you posted shows it. That macbook is way more portable than the MBP.
They are also the same weigth but the MacBook Pro comes with an LED-screen, which will give you a much more uniform screen.
My screen on my Blackbook is very even, but the LED screen does have its benefits such as improved battery life. Also, the MBP has a higher resolution screen, so if you have good eye sight you can fit more things on the screen than if it were lower resolution.