I've had Nike watches since they first came out, and I find I've become quite attached to the Nike faces. I'm tempted by the new blue S6, but I quite like the new Nike Compact face that just got released in Watch OS 7.
What many, but not all, Nike faces do is have a complication to the Nike running app built into the watch face. This basically gives you an extra complication slot if you use the Nike running app, and want a watch face with that complication. So the Compact face has three complications, but with the Nike Compact face, tapping the clock takes you to the Nike app. So with the regular Compact face, you can add Nike app plus 2 other complications, but with the Nike Compact face, you have Nike app plus 3 other complications.