Your first question involved a Dado cut with a Dado blade set. Now we drift off to Router jigs...(?) Remember that unles you have clean sharp bits , you will get the same tearout. I do both types of Dados TS w/Dado blade set and Router with a jig. They both require that the bit fits the thickness of the materials (often today's wood thickness is as varied as the opinions on Global Warming) A limitation that the Router bit has a harder time correcting w/o a tracer collar and a lot of extra figuring (brain thinking often clouds my mind)
Dado sets with shims can address the different sizes with less confusion.
Bill,I have to respectfully disagree with you about the router jig requiring more complex figuring than using a dado set.
I have made and used both types of the router jigs shown in the above posts, as well as many different dado sets over the years, and have two good dado sets now, but I must admit that I rarely use them any more. I do highly prefer the one that Glen showed, that uses the guide collar because ALL routers are not round, (and some even have one flat side) and that means you must keep the same router orientation all the time or the cuts will not be true, and also the router bases seemed to me to have more "Drag" on the sides of the jig than the collar does.
I like to make the jig to use a 1" guide collar and a 1/2" bit, (doesn't matter what kind, straight bit, pattern bit, spiral bit or other as long as it is a true 1/2" so it will match the jig).
To use the jig, you simply clamp the lower edge of the guide to the line on one side of the dado to be cut, then place a scrap of whatever wood you will be fitting into the dado, (making sure it goes most of the length of the dado, OR use a shorter piece at each END of the dado, then slide the other guide up against the scrap and fasten that side of the jig, (as in Glen's jig) or just clamp that side down, then remove the scrap and rout along one side of the jig and then back up against the jig's guide on the other side, and you have a dado perfectly sized to the thickness of the wood that you will be fitting into the dado. I don't know how it could be any simpler OR faster. (and ME,.... I Like Simple)
One other thing about using the router jig is that if it is made from stiff, solid material, I think it helps keep down tearout when it is clamped snugly to the material being cut, kind of like a zero clearance insert.
The SECRET of these jigs that make them so simple to use, is that the bit is always a smaller diameter than the dado width to be cut, and you make a pass along each side of the dado jig. (If you were making a dado smaller than 1/2" wide, you would need to make a new jig to use a smaller bit, probably a 1/4" dia bit).