I switch between watch faces throughout the day. I prefer the high-information faces while I'm at work, so I swipe between an Infograph face and a Modular face (because the modular face can show a couple of complications that don't yet work on Infograph).
In the evenings I prefer simple watch faces that display less information. I might choose an elegant Simple or Utility face, or one of the animated faces like fire, water, jellyfish, or butterflies.
I sometimes use the Siri face, and I have a couple of faces for specific situations. I have a travel face with travel-based complications, and a shopping face with apps I use while I'm at the grocery store (Complications for Bring, texting my wife, etc.).