They are both huskies. As I said, I "usually I hold Kaytu back a little so Nali is more in front ." Denali (the white one) is not a fast as Kaytu. I forgot to add the pic though! I'll edit the first post and add it. I keep both of them in front of me, I don't like them to be beside me like Denali is in the video. They should be in front! They both have harnesses because if they were pulling using a collar they would destroy their necks and choke themselves to death. They must have harnesses to run.
The different harnesses are because Kaytu pulls, and Denali doesn't- or does very little. The X-back harness like Kaytu has is excellent for pulling, but if the dog is not pulling then it bunches up and does not fit right which is why I got the urban harness for Denali.
Kaytu seems to do fine in the X-back but it does have a steeper angle. I haven't tried her in the urban harness, I'll give it a try next time and let you know if I think it was better or not. I actually do have a GorillaPod!!! How did I not think of that? Derp!