I think it depends upon the treadmill. I've found that they are all calibrated slightly differently and a given pace on one will feel different on another. My treadmill at home, a TRUE 540, seems to read "slow." That means if it says I'm running an 8:30 pace, I'm really running closer to a 7:45 or 8:00 pace. I've confirmed this through years of use and comparison to the actual pace I'm able to attain at a given level of exertion running outside. Other treadmills I've found read closer to what I feel is the actual pace for a given level of exertion.
I do find running on the treadmill much easier on my planar fascia. After being almost exclusively an outdoors road runner and race for 7+ years, I developed a horrible case of planar fasciatus that took me months to get over. I've since found that running on a treadmill is much easier on my feet, primarily my left foot, than running on roads.