Maybe I shouldn't chime in on this thread because my outspoken views have a tendency to jerk the chain of some of the other forum members but here goes anywho. I have both the PC 4216 and the Leigh D4R and they both have their uses. I like the PC 4216 for its size when doing small projects and the Leigh D4R for its versatility even though it takes up much more space than I like. As stated before the only major downside to the Leigh products is the cost compared to other dovetail jigs. Just remember they all do exactly the same thing, they all cut dovetails and that is the one thing most people that prefer the Leigh jigs won't accept.
I haven't had any experience with the PC Omnijig but from what I have read I would choose the Leigh and the price differential isn't all that much for the versatility of the Leigh. Looking back over my post I don't think the word "versatility" is the correct word to use in describing the Leigh. My PC 4216 will do exactly the same as the Leigh, cut dovetails of all styles, but it isn't as easy to set up. The one thing I have found the Leigh D4R will do the PC can't is one pass half blind dovetails. All in all if your budget will justify over $1000.00 for the jig and accessories go for the Leigh D4R jig.
When something is advertised as being foolproof there is always a better class of fool that comes along to prove them wrong.