The main difference is accuracy. The Wiimote can interpolate gestures from the data collected from its internals but is unable to do 1:1 motion representation. The Move's tech demos are a great demonstration of the accuracy of the device. Motion Plus (damn plus sign didn't show up) improved this accuracy and is now more accurately able to represent a motion but not much exciting software is out which supports it.
That is the second differentiator: software. Nintendo and third party efforts haven't put a big push behind finding exciting ways to incorporate greatly accurate motion based gameplay mechanics into a broader gameplay experience (I haven't seen much that impressed me besides Red Steel 2 and Skyward Sword), Sony seems to be pushing this in full force by putting it (whether you think it's great or shoe-horning it) into well known franchieses (Killzone, RE, Heavy Rain) as well as new IP's built around implementing motion controls in new gameplay situations (Sorcery).
