The Google Cloud Platform exams do have a lot of comparisons to the AWS exams. Still, in our opinion, for most people, the GCP-PCA Professional Cloud Architect exam will be more complicated than the AWS Certified Solutions Architect Professional exam.
One difference is that Google expects every Solutions Architect to come from a dev background. Now, this might not be an issue for most people, but some would be entirely thrown off by a question asking them to debug some Python code that has nothing to do with GCP.
But this leads to the vital difference: the GCP-PCA certification revolves entirely around professionally performing the Cloud Architect role rather than around the platform itself. There is significant value in this because it can better represent real-world ability. But this can also make it much harder because the scope is almost limitless. Many exam questions have nothing to do with Google.