Either one. (smooth or tooth) The ones with teeth are able to cut harder soils.
Thing with a disc is that you do need to come back with a spring tooth harrow or similar to bust up the clods. You may also have to mow it down tighter and it is harder to turn over growth. So, you may have to use a bottom plow first, then the disc then the harrow to get the same field conditions as the tiller.
Biggest plus with a disc is the rocks don't beat the snot out of them so bad. Then again, smaller rocks (6-8" and smaller) will get shot out and lay on the surface after tilling so if you want to get rid of them the tiller helps.
It's sort of a 6 vs half dozen thing. Each has it's own strengths and advantages.
jb