On the zero clearance insert. It's well worth the time or $ spent. Especially if you do small pieces. If you get a dado blade, you will want to make another for that. Obviously the normal insert will not work if you get into larger dado sizes and the entire gap left from no insert at all is pretty wide. Unless the pieces being cut are big, it becomes more of a necessity than just to prevent chipping.
If you make them. Do be careful and use a VERY sharp blade and strong clamps. Starting with a thin blade like Fred mentioned is a good idea as well. I tried it with my old utility blade in and once it got so far it started pushing vs. cutting. Switched to my new kerf blade and the problem went away.
