That's sort of like mine, it's mostly jsut because of the pixel pitch. My m1330 has a 1280x800 screen, my desktoip display is a 20" with 1680x1050. The laptop seems to have a nicer image, because the pixels are smaller, and on comparison with a friend's m1530, hers having the same 1280x800 native res, mine looks better. It depends upon your laptop though, especially if it has a very high res screen.
There's also the big point of: inside that display, it's likely got the power supply inside, along with stuff to actually get the display to work with different inputs. For example, your laptop's screen only has one input, direct from the graphics card, and the power is supplied to it at the right voltages already in most cases, meaning a lot of the circuitry is no longer necesarry.