Looking at this more, the degradation over time seems to be the main issue. When I first load a dashboard in Firefox, it's reasonably snappy, in the same ballpark as Chrome. After a day or two, though, it's really slow.

Those are Google apps made for Chrome and will run better when using Chrome. Firefox can't program for Google apps.

Thanks for the reply. I definitely get the concern! It's drastically overstated, though. I use dozens of other Google web apps on Firefox perfectly fine; this is the only one, and the only feature inside it, where I notice this kind of Firefox-specific performance issue.

I spent 10 years working as an engineer at Google. I know from experience that they want their web apps to work in all browsers. People there obviously do use Chrome more day to day, which can lead to subtle issues like this, but it's generally not structural or intentional. Google Cloud Monitoring dashboards don't deliberately include some performance degradation and then use a secret, Chrome-only API to prevent that degradation only in Chrome.