more or less wire leaders will hinder the action of the lure. I find that it has the least effect if you use it with lures that is constantly retrieved (i.e. spoons, in-line spinners, spinnerbaits, etc). For jerkbait and crankbaits, the wire leader weight down the front end of the lure so when you "pause" it, it tends to sink the front end.
I have heard good things about heavy flouro leaders but I have never used it myself so i won't comment on it ...