https://www.youtube.com/watch?v=2ixCHEgjlWE&app=desktop Just at first glance which dog would you say is getting the better workout ? I would have to go with the dog on the carpetmill as he seems to be putting in more effort to push and takes longer strides which in turn works more muscles more intensely and works on his cardio at the same time. Dog on the slatmill seems to be gliding by with minimal effort which in turn gives less of a workout, im not knocking slatmills in any way im sure they are a useful tool, just my observation.