You know I thought about this treadmill vs outside debate and here is what I have come to think:

Its about weight. THe heavier one is, the easier running on a treadmill will be. I think this makes sense logically. Empirically, I certainly remember having a much easier time running outside (and comparatively harder on a treadmill) when I was in tip-top shape weighing in at 145 with a very low body fat percentage. Today at 176, running outside is harder -- or at least I am slower -- than running on a treadmill.

How does that strike you?