I think if you ask better golfers, controlling the distance is a lot harder (and more important) than the line. When I'm looking at a difficult approach shot, I'm always going to aim to a safe target and make an aggressive swing to that target. I'm giving myself room to miss the line a little, so if I do I'll probably still be in a position where I can make par.
Missing the distance is a lot harder to predict and control. A slight mishit, or misjudge of the wind, can result in being buried in the lip of a front bunker or hitting the back slope of the green where it kicks down the hill into trees. It's especially tough to guage distance when you have an elevation change--even a solid shot that you hit "perfectly" could end up sailing over the green into trouble.
I've always felt like my best iron-play is when I'm consistently hitting the distances I want (maybe not exactly pin-high, but at the distance I was targeting) because that means I'm making good contact all day. I can correct an alignment issue pretty easily, and a solid shot where I missed my line is still probably going to be inside 30' which leaves a realistic chance for birdie. A slightly thin, toed, or chunky shot might be only a few yards off-line but well short; likewise when you pull the wrong club (or worse nuke an attempt at a 3/4 wedge) you're almost never going to be on the green.
Just ask Phil after hitting wedge to the short par-3 13th at Merion. Pin high (or hitting the right distance) is huge.