The choice is yours; with one screen you maybe more efficient with energy and the desktop, while two screens can help a lot. In this latest article of mine, I shall give you pointers about 1 and 2 monitors/screens.
One Monitor
1.1 Overview
When you use only 1 monitor; it is easier to manage all your files because of your taskbar will only ever appear on 1 screen (main screen). It also wastes less power so there is less contributing to global warming.
1.2 Pros
Efficiency; less power is being used and that when you move things around on the desktop it's easier to find when only using 1 monitor. Another thing which I should mention is that you don't even need to have a GPU and that it is faster than using two monitors with extended desktop (makes desktop both screens). Some systems are not compatible with two monitors for instance; Mandriva (Linux).
1.3 Cons
When doing projects it's harder because you have to keep switching between your programs to finish you work. As in the next paragraph I state that in different cases that if you use more power but you are using less it could mean you helping reduce greenhouse gas or you could be increasing it.
Two Monitors
2.1 Overview
When you use two screens it can be efficient by making effects to the time you are on the computer and/or finish your project/work in, but can work only with a GPU/Graphics Driver. It effects the environment by using more power it creates greenhouse emissions. Although one can argue, that if you use something less but have less efficiency when using it. So it's your choice buy what you want.
2.2 Pros
As I said in the overview you can argue it makes more because you are using more power but you are using less so in some cases it means that you are helping reduce greenhouse emissions. You can quickly and efficiently finish your projects/work by using one monitor to research information and the other one to do/edit your project/work.
2.3 Cons
Some systems are not compatible with two monitors for instance; Mandriva (Linux). I have not tested Ubuntu, Kubuntu, Debian, Gentoo or any other Linux system on my 2 monitors. The taskbar (Windows) will only ever come up on your main screen; the one you use to log on to Windows.
So it's your choice, what you think you do.
