Color me surprised! I would have seriously bet that Chieri would have been the first to get animated. I remember hearing that it had a much larger readership, and it seems like it would have been a much "safer" pick, being more or less a conventional "dream girl" series in the vein of Komi or Uzaki.
This might be a bit bad mannered, but I'm actually kind of glad Oriko's the one hitting the screen instead of Chieri, largely because Chieri is so much "safer". I think Oriko is likely to be a lot more memorable in the eyes of viewers who aren't already deep in the giantess rabbit hole and inspire a wave of giantess-focused imitators, in a similar way to how Monster Musume sparked a monster girl boom back in 2015, or how Onimai sparked a TSF boom. Chieri, I think, is too conservative to have the same effect - it would be a lot of "the giantess gimmick is fun, but I've seen all this before" and kind of get lost in the sea of all the other cookie cutter "dream girl" romcoms.
I'll still watch Chieri if she ever does make it to the screen, but I'm definitely a lot more excited to see Oriko come out ahead and get first dibs on a TV adaptation. Now excuse me while I go pop the biggest bottles.