Well, honestly, if I knew EXACTLY why I would tell you why. But, from experience, it is tough to beat a shiner with a plain red hook and a split shot while fishing deep on Mille Lacs.
Once you get up on top of a flat, 24ft or shallower, I have yet to find anything better than the Jig-a-bit. For me it was just a matter of trial and error and fishing on the Mille Lacs a lot. 24 ft is kind of a magic depth on Mille Lacs. The water deeper than 24ft fishes much different than the water shallower. Some has to do with light penetration, some has to do with the attitude of the fish that inhabit each depth and their food sources I would guess.