What's the most important aspect of shooting? Other things being equal, it's distance - how far you are away from the net. Once you take hundreds of thousands of shots, all of the things that might impact shooting percentage, like shooting angle or screens or 2-on-1s or individual shooting skill or goaltending, are a wash. Here's a chart that shows that relationship:
There are only 1/3 as many shots at 5-on-4 as at 5-on-5, so the PP curve isn't quite as smooth as the ES one. But the behavior is the same - continuously increasing from the blue line right into the crease, with shots slightly more likely to go in on the PP than at even-strength.
Every player understands this implicitly and obviously tries to get as close to the net as possible before shooting. It's why forwards score more than defensemen. But it's not clear if shooting distance is something forwards can actually reduce, or if it's in their best interests. Shooting distance stats by shot type are available here for forwards for 2007-08 and 2008-09. As I noted in Part 3 on Corsi Numbers, shooting percentage is heavily-influenced by luck, while shot volume is often a better indicator of expected performance.
Looking over the average shooting distances for defensemen, it seems like they might have a bit more control over how far away they shoot from. On the 2008-09 list, part-time forwards Dustin Byfuglien and Mathieu Dandenault are 1-2, with Dan Boyle at #3, while they're 1-3-5 in 2007-08. Boyle being #1 among full-time defensemen isn't surprising, but at the same time, there are plenty of defensemen with some offensive skill at the bottom of the list.