GCP got really, really good in the last few years. The cross-account story is now better on GCP than on AWS. BigQuery, Spanner, Pub/Sub, GKE are all best-in-class. AWS has its advantages too: CloudFront, Lambda, S3, DynamoDB, and IPv6 support are all best-in-class. It really just depends on what your product's actual architectural needs are, and whether you have access to nosebleed budget to pay for it all (these services are all staggeringly expensive).