What exactly is your threat model?

In terms of technical implementations, Chrome naturally surpasses everything else in a naïve myopic comparison (and always will), but holistically a secure algorithm isn't going to protect you if you've voluntarily handed the keys to the kingdom to umpteen untrusted parties. Chrome gets all the technical details right in a context where doing so seems redundant.

With the exception of your personal stats.

It makes perfect sense if you're less worried about your internet usage privacy than about browser exploits installing malware onto your computer.

Then “security” is too vague and needs to be qualified.

Sorry but this is a bit clueless, what are you trying to secure exactly, if it's not your own data? You can't honestly thing that data is safer in Chrome than Firefox.

I doubt google engineers rank high in his threat model. :-)

Firstly, why just Google engineers? Many Google employees and any 3rd parties Google share data with would be included.

Secondly, that's a single step in the threat model; it's not just about what a Google engineer would do with your data, it's about attack surface area when any Googlers (or Google infra, or Google partner infra) that is compromised automatically exposes you.

The simple act of transmitting and storing your data to anyone, no matter how secure their systems are, is still by definition less secure than simply not transmitting that data.