Lots of things you can use for priming. I use corn sugar simply because I always have it on hand (of course, if I switched to table sugar I'd probably stop always having it on hand). Either or will work, as will just about anything fermentable (DME, LME, wort, honey, maple syrup, molasses, agave nectar, etc etc etc). The primary concern is that you're using the appropriate amount for the carbonation you want. Most calcualtors will have figures for DME, corn sugar, and table sugar. They may not always have an alternative priming source if that's what you want to use.