How much room for blogging?

I got to know that even though you are using a 15' inch wide notebook you do not need that much space to blog at all. The screen is wide but the space of what you are using are still the same. There is a big space on the right which you can see clearly.

Now 14' inch wide notebook will be just nice! But 13' inch will be good too. It is depends on your like and features you are looking for.