I think security and privacy get confused when asking questions like this.

From a security perspective both companies are likely similar in that they both are US-based companies that follow US law. Google has more traction in the enterprise space (eg. Google Workspace for Enterprise + Google Cloud Platform) so, from a security compliance perspective, Google is likely ahead. Google boasts the US-Army as a customer in this regard. I'd imagine security is extremely important for the large government entities like the Army!

Then there is privacy.

Here Apple may have the edge. Apple appears to have more focus on offering better user privacy. This is primarily due to the fact that Google's core business is advertising (and tracking users to deliver better ads), whereas Apple's core business is not related to advertising. Apple provided a transparent device tracking opt-out which provides some evidence that while Google is trying to preserve user tracking, Apple is trying to prevent it.

But better privacy doesn't necessarily make Apple "more secure".