The only one I can tell you about, and the one I'd choose if security updates were uppermost in my mind, would be any Pixel. The updates come out on the first Monday of every month. Also a good antivirus,
Malwarebytes Anti-Malware and safe surfing techniques (which includes Bluetooth and your SIM card).
Many companies are given the updates about a month before Google releases them to users, so that the companies can modify them to install on their devices and still release them at the beginning of the following month, but that doesn't mean that the users get them at the same time as Google users do. (And waiting for the normal OTA update can mean a month's delay
after the company releases it - OTA updates are staged. Being able to download the update and install it yourself - as you can do with Google's phones - means that you actually get the update at the beginning of the month. I'm sometimes busy and don't install it until late Monday or even Tuesday, but that's on me, not on Google.)
ASUS? I've had dealings with the company. They don't seem to take the "service" part of customer service seriously. (Google definitely does - I think their script reads "if it sounds legitimate, offer to replace the phone". They've actually sent me replacements for problems I finally managed to fix myself [and as a retired engineer who used to design electronic communications devices, I don't call them with the easy problems] and told me to just refuse the replacement [which they're paying round trip shipping for). ASUS? I had a desktop of theirs that had an ISA drive port - but it didn't work. When I called and asked about getting a replacement, I was told that the user isn't supposed to open the case. Really? Was I speaking to customer service, or the office maintenance service?
Xiaomi I have no experience with.