Calorie discrepancy between treadmill reading and pedometer?

I harbor some distrust of treadmills, so I guess the question is this: when you are using the pedometer, are you walking outside on a road? I was road running 3 miles every other day up until November of last year when I took it inside to the treadmill for the winter months. While inside, I continued to run at the same pace- 6mph for the same amount of time. In April when the weather turned nice again, I took to the streets and was dismayed to discover that I could barely run for half the distance without wanting to keel over and die.

Why? Running on a treadmill is easier physically because there is no resistance and it actually helps you by propelling you along.

Personally, I would tend to trust the pedometer as more accurate, myself. My trainer at the gym once joked about how you can't trust the machines to be terribly accurate and I've noticed that when I workout at the exact same level on one elliptical machine, the workout nearly kills me. If I move three machines down and do the same level, it's no problem.

Then again, I've also had the pedometer on my i-pod be wrong too--it thought I had covered less distance than I actually had. (and I had used my car to map out my running route so I knew exactly where my 3 mile finish line was). Unless my odometer is wrong. Argh. Technology!! I dunno. Maybe take a happy medium between the two? lol.