I’ve never seen a statement like this before:

Cirq is currently in alpha. We are still making breaking changes. We will break your code when we make new releases.

The emphasis on “will break” is from Cirq’s GitHub, not from me. Also from Cirq’s GitHub:

Cirq is not an official Google product.

This is a screenshot because I merely copied-and-pasted some sample code. I did not modify it any way; I just wanted to see what would happen if I tried importing and using the Cirq library. It seems to have done what it was supposed to do, even though that circuit diagram is unimpressive.

Anyway, I’m going to declare this an easy victory for Qiskit. Comparing and contrasting the two libraries is completely unnecessary. Qiskit is in use at international competitions (hackathons) and universities and research facilities, while Cirq is guaranteeing that any code you write today will stop working in the near future.

It is also worth noting that Qiskit can access real hardware. As far as I can tell, Cirq is simulation only.