Ok, just asked because the walnut version of same grit showed up on Amazon. Walnut has always been my jam!
Walnut = dust. That's the big difference. Corn cob - no dust. Charge it with case polish of some sort (I've been using Dillon for years because it works well) and you'll get bright shiny clean cases with no dust.
Sticking in the flash holes is a function of the size of the media. The corn cob I'd been using for years from the local gun shop never stuck in a single flash hole. Then that source dried up and I tried the Lyman corn cob - it sucks balls. Sticks in the flash holes AND they didn't bother to clean the chaff out of it, so there's all these fine flecks that stick all over the brass. People who claim corn cob is bad probably got stuck with that crap; I'd hate it too.