Because of these questions, I have now downloaded and tried:

Firefox Developer (119.0b1), Chrome (117.0.5938.92), Opera (102.0.4880.56), Edge (117.0.2045.43).

Turning off all other programs (without crashing Windows), ranking for trying to drag the selection square ~2 inches x 2 inches (on a 1920 x 1080 laptop with the above noted characteristics) without doing anything else. Did the drag back and forth TL-BR, BL-TR 5-6 times to get a feel for general timing (cannot claim I used a stopwatch):

Edge: ~1 sec response before square changes

Chrome: ~1.5 sec response before square changes

Opera: ~1.5 sec response before square changes

Firefox: ~2 sec response before square changes

From my super low-end perspective, Edge is surprisingly responsive (maybe optimized for Windows?)

Edit: From another perspective, looking at the Dev Tools (what I actually care about), Edge is pretty hilarious, it has 72 errors on its default landing page (including this is not a "TrustedScriptURL"). Opera only has 2 "Uncaught (in promise)" and both Google and Firefox have 0.

There's something comforting about the idea that Microsoft still does not trust Microsoft. ("Left hand meet right hand. Begone fool, we have no hands!") The more things change...

It was completely unusable on my M1 MacBook on Chrome, I suspect it's hitting some degenerate webgl/driver edge case.

Strange, was super responsive on my m1 MacBook Pro under Firefox.

Interesting. M1 Pro Macbook Pro (14" 2021) w/ Firefox, massive lag - to the point rotating the view is unbearable.

For the dev, FF 117.0.1 on macos 13.4.

Same here on M2 MacBook Air.

AFAIK, Firefox has all around awful webgl and webgpu performance.

I know personally, anything 3d in Firefox is a slideshow, even with a 4090

It's running quite well here on Firefox in Fedora 38 with a AMD Radeon 6700 XT.

I have an AMD 6700xt.

It was laggy in Windows and under X11 on linux, but under Wayland I get 60-80fps and it's very usable.

Not sure what the cause is

EDIT: Under Chromium (compiled from AUR) the performance is roughly the same

Works fine for me running Firefox in Windows with a 3090. Also already have Unreal open on another screen. So lots of my GPU memory is already being eaten up.

In Firefox on a 12th-gen Framework i5-1240P, Fedora 38, integrated graphics at 2256x1504, it works and looks fine for me.