Since the difference between those two models doesn't appear to be in their geometries, it may have more to do with frame construction and material. Perhaps the Amira is a bit stiffer, while the Ruby is more plush. I've never ridden either one so I don't know first hand. A stiffer bike might feel like it handles faster or twitchier. If you can, test ride both.
Live with intention. Walk to the edge. Listen hard. Practice wellness. Play with abandon. Laugh. Choose with no regret. Continue to learn. Appreciate your friends. Do what you love. Live as if this is all there is.
--Mary Anne Radmacher