For a mid sized laptop, you can choose one that is 15.4 inches, 15.6 inches, or 14.0 inches.  These laptops are great for general portability.  They weigh a bit more than the 13.3 inch and 11.6 inch laptops, but you get a larger screen size for text and graphics.  If you want a bigger screen but also want to minimize weight, then opt for the 14.0 inch laptop.