Laptop is more energy efficient than Desktop as it uses 5 times lesser energy than a PC. A laptop uses around 15 - 30 Watts of electricity whereas a desktop uses around 100 - 150 Watts of electricity.
Even if someone plans to buy a desktop then better to go for a a LCD screen than a normal CRT colour monitor. Since LCD would use around 30-40% of power used by a CRT monitor. For example LCD would take 40Watts compared to around 100 Watts of electricity by CRT monitor.
Laptop is designed to run with battery most of the time, so the energy quotent is very low while designing the desktop there was no such consideration in mind. THough it is always suggested to enable to energy saving ode for the PC.