In my case, an example of a non-exotic site is Youtube streaming 4k 60fps videos. I tried with latest Firefox a few months ago and it was still stuttering and glitchy. But Chrome plays smoothly with no issues. I previously mentioned that 4k playback has been a long-standing issue: https://news.ycombinator.com/item?id=28783904
On one hand, my computer is fairly old ... but then again, Chrome works fine on that same old hardware.
What firefox cannot do and chrome can is HDR playback.
No, even if I download the 4k 60fps file using yt-dlp with forced h264 codec settings locally to my harddrive, Firefox still can't play the mp4 file smoothly.
So it's not really a streaming issue or h264 vs VP9 codec issue. The Firefox core engine doesn't seem optimized to playback 4k and 8k high-frame-rate videos with low cpu utilization. Even VLC for 4k and 8k isn't as smooth as Chrome. I don't know what the Chrome team did but they really optimized that code path to play back hi-res videos.
Oh and a while ago I noticed (on a more modern system) that enabling hw decode makes chrome ignore the aspect ratio of the video and displays it like the pixels are square. Again Firefox handled it fine.
(Linux, h264 in both cases)
And look no further than Google themselves: https://labs.google.com/search/install
I'll give you one example: I sometimes can't open OpenAI API documentation due to some stupid Cloudflare captcha checks. No, on Firefox, however many times I click that checkbox, I can't go through the verification, just to read some static content. Not even if I disable adblock and tracking protection.
I don't even see a checkbox at all on Chrome or Edge.
Sure, technically nobody is excluded: Just solve the captcha! Fraud heuristics are only reasonable, right?
But it's all fun only as long as your situation occurs within the 90th or 95th percentile of all data labeled "good customer". Good luck if you're out side of that...
I mostly use Chrome on Linux (fully Google distributed, closed source Chrome...so not Chromium) and I see those cloudflare captchas at a much higher rate than I do when using Windows or macOS.
Enabling JS is not enough, so I think its liked to privacy plugins, or running inside a container.