I've seen recipes that call for priming with either. Is there a difference in the final product? Would you use one or the other in different style brews?
1lb corn sugar in 1 gal water will provide 40 gravity points, or 1.040. DME will make 45 points per gal. 3/4 cup of corn sugar will generally give a nice volume of carbonation. Since DME has more points you would need to use a little less. I think DME might take longer also. I've never used it corn sugar works fine. You might want to check the recommended volumes of carbonation for the style of brew you are conditioning. I will recommend sticking to corn sugar, its cheaper, works just fine.
Unfortunately it calls out volumes. Anyhow it calls for 1-1/4 cup DME. I heard people us as much as 1-1/2 cup, like Cheesefoods VCCA
I like to use Munton's Kreamy-X on some brews. It has corn sugar, DME, and heading powder. It give the beer a thick mousse head and it leaves lace all the way down the glass.
I used it in my Vanilla Caramel Cream Ale (see picture above - courtesy of cheese) and me pub ale. Its like a poor mans nitro.
Actually, you usually need to use a little MORE DME than corn sugar when priming, since it contains some unfermentable content.
If you want to stay true to the Reinheitsgebot, use DME. If you want more consistent, faster, cheaper carbonation, use corn sugar or carbonation drops.