I feel more power in my legs, doing hill repeats, more than doing stair repeats. Both are awesome, but hill repeats have my vote as best. If your gonna do the stairs WALK them. Get the feel of it! You're working the same muscles. I have noticed pain, after comparing walking them, and running them. You also don't have to RUN hills, to get a hill workout in. My last race Hibiscus Half Marathon, I trained by walking hills most of the time, but don't get me wrong, I did RUN them also.