The treadmill becomes more of a regular thing for me in the winter, darkness pushes me indoors for my weekday runs. On the weekends, you'll only see me on the TM if there is ice on the ground! I get so so bored!

I think each affects my joints differently. On the road/sidewalk I have more discomfort in my ankles from the pounding on the hard surface. On the TM my hip issues flare up because I tend to run pretty awkwardly on the TM.