edt's have better sillage ie. they 'waft' better but don't last as long. EDP's/parfums, last much longer, have less sillage, are softer and stay much closer to the skin, and often are better crafted ie. a few notes are often substituted for higher quality products so that the scent is more rounded/full bodied. Basenotes (the fixative which adheres the top and mid notes to the skin) are the most often substituted.
You may find you don't like the parfum/edp as much as the edt and vice versa, use whatever you find smells the nicest.