Running versus power walking

Neither is necessarily "better" from a weight loss standpoint. The fitness training effects will be slightly different, but might not be significant to a particular individual.

Burning calories is a matter of intensity, not activity. If you can achieve a similar intensity with different types of exercise, you will burn roughly the same number of calories.

Especially if one is a slow runner, it is possible to achieve a similar intensity through incline treadmill walking. You have to train yourself to handle the incline for a sustained period of time (interval-type training can be helpful in this regard) and you CANNOT hold on to the handrails. Holding on to the handrails can decrease the intensity (and thus the calorie burn) by as much as 70%. Basically, if you cannot keep up without some type of handrail support, then the workload is too high.

I find it is easier to walk at a lower speed and steeper incline that it is to "powerwalk" at a more modest incline.

No cardiovascular exercise will do much for "toning". That requires some type of resistance exercise.

There was an actual test done on Runners World magazine, I think. The conslusion was that running is almost twice as intense in terms of calories burned. They did several different kinds of tests to come to that conclusion. It's published, so probably some kind of Google search will get you there. But, on a treadmill, I don't know. That's so different than running or walking for real. The treadmill moves your feet for you, rather than you moving yourself forward.

If I run a mile on the treadmill at 6mph at a 1% incline I burn about 105 calories (per my HRM). If I walk a mile at 4.2mph at a 7% incline I burn 155 cals.

So for me, I tend to power walk more than I run nowadays.

OK. I get it now. But, you are comparing apples to oranges. If you ran @ 6MPH at a 7% incline, how many cals would you burn. Way, way more than power walking. I totally get the question, but ...