I think the walnut media is a bit more aggressive but doesn't produce a nice shine like corncob media. I'm betting it will do a more complete job overnight.

I tumble overnight and have been doing so for twenty years with the same vibrobowl.....it's still running great. I agree....do it on a concrete floor!

I like clean more than shine.....so I use walnut!.....and yes....you can get very clean with corncob too!....just sometimes takes longer.