As they say! Think "portable?"
A friend of mine bought a laptop, a fine thing with a lovely big screen.
It's too big to carry around, so he effectively has two desktop machines, one in his study and one on the dining room table (much to his wife's annoyance).
Now he's looking to buy a real laptop that he can carry around and use.
Mine's got a 13 inch screen, and I find it ideal. (It's sold as some other size, but the folks who measure TV and pooter screens use different inches to the rest of us).