The stinkier the better. Ever watch any episodes of catfish noodling? Those guys are crazy.
Yeah, noodling is “another world”. ;-)
Stinkbait (or dead bait fish going slightly bad) works well for channel catfish around here (mid-South) from mid-June into mid-Fall. But my best success has actually been with live crayfish - when I can catch some. My suspicion is that they fight the rig they are on and create lots of vibrations in the water.
Larger channel cats and blue cats lean more piscivore, and flatheads are almost entirely piscivores, but will hit fresh cut bait. The biggest fish I’ve ever caught, coincidentally exactly 36” long, was a 36” flathead that hit a 1” x 4” slice of bluegill. Generally I don’t target the “big ‘uns”, as the 2-5 lb. fish taste better and are lower in contaminants. Above 8 lbs., for a catfish, I practice catch and release. Hopefully some of the blues and flatties will get big enough to cut into the Asian Carp populations...