Hi: I have the Leigh jig and it's very good. I have had the keller jig, and an old Stanley
jig. I like the Leigh because it does through dove tails as well as half blind and can also do sliding dovetails. All of the comparisons I have seen in the magazines gives the Leigh the highest ratings, The documentation is excelent. I have no info onthe Incra jig. Woodnut65
I have the Incra origional Universal Precision Positioning Jig on my router table. I got the jig and fence at Rockler for $99. The jig by itself is only about $50 and you can make your own fence.. anyway the jig is great. It does box joints and any kind of dovetail joint (through, half blind, sliding, double, etc.). On the other hand.. If you are lucky enough to afford the LS system, IMHO, there is no more accurate system out there.
You can check out the details and see a video on the origional jig at Rockler.com:
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