I've made a lot of box joints over the years, using many methods and jigs. Some years back, when the Incra I-Box jig became available, it's inventor (a friend and club member) gave me a demonstration of it's features, and I had to have one. Using it on a router table cut the joints well, but I was not happy with the tear-out, because the spinning bit is cutting both forward and back at the same time, so a sacrificial backer (zero clearance insert) isn't easy, since it needs to be on both sides of the work.
Cutting them on a table saw with the blade always cutting in the same direction through the wood only requires a sacrificial backer on the side of the work where the blade exits, and this sacrificial backer is an included feature in the I-Box jig. You just position it to an uncut area of it when about to begin cutting a new size joint. The first cut makes the required zero clearance cut through it and can be used over and over as long as you don't change the blade height or the blade set width. This sacrificial strip is just a piece of 1/4" thick MDF, so replacements can be made easily, using the original as a template, but it can be used many times and then inverted and used many times again before it actually needs replacing.
I have the Freud XBOX-8 blade set for 1/4 and 3/8" box joints, and also a Freud Ripping Blade with a 1/8" flat bottomed kerf cut, that I use these for most of my smaller box, box joints. For large boxes and larger box joints I use a Freud Dial-A-Width blade set. It has the bat ears, so doesn't make perfect box joints, but in larger boxes and joints they are less visible and so are acceptable to my needs.
I've tried many ways, even own a Leigh D4R dovetail jig and special box joint top plate, but I get better box joints with less tear-out by using the blades and jig above on my Unisaw. Attached are a few photos of some of my box joints. After buying the I-Box jig, all of my DIY single size box joint jigs went into the burn pile. Some worked great, some not so great, but the I-Box Jig is easy to adjust for different sizes and does a better job. It takes up less shop space than that stack of DIY Box Joint jigs too. It's so convenient to use that every box gets made with box joints, unless dovetail joints are a design requirement for the project.
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