I was seaching and came upon this thread... I have both the Porter Cable Omnijig and Leigh. Price-wise they are nearly identical (when you puchase the optional templates for the Omnijig) and there is nothing the Leigh jig can do that the Omnijig can't do... the only difference is that with the Omnijig to get variable spaced dovetails you need the optional template. They both work very well and I'd give a slight edge to the Porter Cable for easy of use and repeatability.
FWIW, the PC 7216 can cut variable spaced through dove tails. See attached picture of variable spacing template.