- Both run proprietary versions of in-house developed software (iOS and Android with Google Play Services)
- Both have on device security management software solutions (Secure enclave and Titan M)
- Both have heavily regulated app environments (iOS's closed App Store vs Google Play Protect)
- They both receive timely security update (iOS on demand updates and Android's monthly security patches, which appear first on Pixel)
- Both farm out their cloud storage to other companies and neither are encrypted.
One thing to keep in mind with Android is it is based on an open source platform. As such, more people are more heavily invested in its security. Vulnerabilities are more difficult to find for everyone on iOS which is a double edged sword. Generally, that means if someone does find an iOS vulnerability (which people certainly have), it takes longer for it to become exposed because there are fewer white and grey hat hackers looking at the codebase.
There are certainly counterpoints to this, and SEVERAL of these arguments do not apply to OEMs like OnePlus and Samsung, but the Google Pixel line of phones is very different and much similar to iPhone in terms of security.