In addition to the fact that Kygo I is based on an earlier version of U2's track, I also think there's a certain degree of "improvisation" that occurs during a live DJ mix. So it's not likely that the remix that was released last week would sound exactly like the live version anyway.
I have another theory about the mixes of this song. In a couple of the radio interviews, both Bono and Edge mentioned that the version of "You're the Best Thing" they were planning to release was more smooth and polished, and at the last minute they stripped it back to more of a band sound. I think the "Sci Fi Soul Mix" is probably the smoother version. In other words, I wouldn't be surprised if the "sci fi soul mix" was actually the planned album version until they changed course at the last minute.