If GP is anything like me, they used Firefox before Chrome was released. The Mozilla/Netscape suite that spawned Firefox is older than Google itself.

For a time, Firefox performed worse than a rabid dog. Chrome ate their lunch and gained market share fast. I and many of my colleagues switched around that time.

In my case: Because Opera stopped using Presto and switched to Chromium. That does says a bit about when I switched.

I used Firefox pretty extensively, then switch to Chrome when Firefox fell behind on speed, but the developer tools absolutely sucks in Chrome, so I tried Opera which had a great feature set, speed and wonderful developer tools. It was a pretty sad day when Opera dropped Presto, and more so when they where bought by some Chinese company.