The difference is quite obvious, at least on Windows. Roboto is narrower, better hinted, has fewer embellishments, got a better consistency ("rhythm") and as a result it's much easier on the eyes. Here, side by side - https://i.imgur.com/tXokROR.png - Roboto at the top, Chirp at the bottom.
It also seems that chirp has unusually short ascenders and larger lobes/bowls. For example the 'h' character looks like a child drew it and much closer to an 'n' than one would expect.
