Google Cloud - Multisite with or without Bitnami

Hi everyone,
I'm thinking about hosting a client's WP Multisite on Google Cloud. But they propose 2 options:
WordPress Multisite - estimated cost is $24.67/month
WordPress Multisite Certified by Bitnami - estimated cost is $14.20/month
I do not understand why the Bitnami version is cheaper and I don't even understand what's so special about the Bitnami version. I assume it is a pre-installed package which is monitored against treats and such... But I'm not sure.

Does anyone of you has experience with one of the versions or is anyone able to explain a bit more about this?
Much appreciated !