Homebrewers - Whats in the fermenter?

Since you're working the yeast a bit harder, there's a potential for there to be a flavor difference, but since we're only talking about a few ounces for priming, you'll never taste it. Using DME could certainly change the flavor since you're adding unfermentables as well. There are people that claim DME gives them "finer" carbonation, as in smaller bubbles, but there's nothing to back that up, and many others that tried it and claim no difference.