Don't know which to vote for!
I mean, Dark Horse is good because it is much more experimental than what Katy has done before, so maybe that's what the public needs. With that being said, We only heard a snippet of it. A snippet is just not enough to judge the rest of the song considering we don't even know how the breakdown is gonna sound

Walking on Air is safer but the public might get bored of it quickly because it is rather classic Katy formula just with a freshened up sound. The Hummingbird Heartbeat that should've been the 6th single teas! We shall see... Gulp. Whichever doesn't win I can see as the 5th single TBH.