I voted baitfish. The waters I fish don't have shad, but the bass are often keyed in on perch/bluegill/ trout it seems. Where I fish there are a ton of crawfish, and I often do well on craw baits, but usually baitfish imitators do best. In the early spring and late fall I usually always catch them on craw baits, and they often spit up craws, so it seems to me like it varies by season. Right now, from what I can tell they're eating a lot of perch and bluegill. Also, my best lures are ones that run higher in the water column and imitate these.