The big portability savings is in not having to carry a computer monitor, and in being able to undock the computer to work on non-LD applications. These are micro-docking stations, which just duplicate the ports on a notebook making it faster to hook up to a desktop configuration. Port replicators have no slots or bays, so they are useless for LD's needs. The screen is important. You also need to check the maximum colors available at various sizes.
Colors are rich and bright, with no movement fade.
Four or five people can see the screen simultaneously, making active-matrix essential if you'll be doing a lot of demos. The XVGA 1024 x 768 screen provides 2.5 times more area than the VGA 640 x 480 screen. Most notebooks can run an external monitor at SVGA resolution. When on the road, the dual-scan VGA screen will be useful enough to edit and do basic changes. This way you never need a monitor, and you can do lots of work comfortably in the field.