I tried both while testing things for a personal project. In my very not exhaustive user perspective, I like Crunchy better.

Zalando seems to fit the Zalando use case (not surprisingly), which is having multiple teams self-service their postgres clusters. They have a nice Web ui that is good for people who are not familiar with k8 to provision databases. However a lot of those features are a bit intrusive when you want to start a small project. The "teams" attributes are required in the clusters, for example, although you're not using them.

I ended up using Cruncy for my personal project because its a bit simpler, looked like having a bit more activity on Github, and slightly better documentation from my perspective.

link to the zalando postgres operator: https://github.com/zalando/postgres-operator

I would like to see a comparison between this operator and Stolon.