Witness is more consistent, easier riding board. It will sit a little deeper in the water and turn a little smother. Most people ride it without the center fin for a more forgiving and quicker release off the wake.
The Harley will have a much more sudden pop off the wake, as well as overall faster speed when riding. The landings on the Harley are very soft as well. It also sits higher in the water so it will turn much faster into the wake.
Both are awesome boards that alot of people really seem to like.
Shameless Plug.... I have a 2013 LF Harley 139 still in the plastic if you are interested