The older, plain 'MouseMan Wheel' and the newer 'MouseMan Wheel Optical'. At first glimpse, if I had to pick by look alone, I'd take the Optical. That cool blue was tough to capture on camera, so I apologize for not being able to do it justice. There is another difference other than just the color and lights of the two. That isn't a big concern but I do like the larger buttons of the Original.
Next issue is the optical reading .
There has been a superstition about the optical mice for not being the choice for hardcore gamers. And it is true that if you move the mouse rapidly, it will not track accurately. This one won't either. I even moved the mouse off the Ratpad that I am using and used the desk, same result. Now, onto some of the features and issues I ran into.