The Loft of your clubs is a very important fitting factor. In the Irons, there are several considerations. Are you a strong hitter of the ball? Generally you can test a decrease in the Loft of your irons. Strong players (think TIger Woods) usually hit the ball high. A more "boring" trajectory can improve distand & control.
For the slower swing speeds and golfers with a smooth transtion an increse in Loft may help with more distance. A higher ball flight creates more carry distance.