I have had a variety of jigs for making dovetails. I hava an Akeda, Prazi Chestmate, Rockler DT Jig and I have an Incra Positioner 27". Of all of the jigs I use the Incra exclusively now. The Incra is so versatile and you can make so many different types of joints. The other jigs I have make good dovetails but you are limited by the dimension of the dovetail. So if you have 1/2" bit the stock needs to be in 1/2" increments. The Incra makes variable spaced joints and is a very versatile system plus you have a very precise system for rabbeting and dadoing which the other jigs cannot do.
I also have an Incra I-Box jig for making box joints. I use a Frued 1/4" and 3/8" blade set with the I-Box and all I have to do is insert the blade on the saw, put the jig on the miter slot, adjust the height of the blade and bam I am making box joints. There is no easier way to make box joints. I primarily make 1/4" joints so if you need to switch over to 3/8" there is a setup and adjustment but if you make 1/4" last time and want to make 1/4" this time there is almost no adjustment except height of the blade.
I have a lot of Incra products and love each and every one of them.