If you are 100% careful, you can get equal performance with a good WebGL implementation, like ANGLE, and good user code. But this is very difficult, and requires very careful programming.

I built a WebGPU-like layer [0] for my 3D web application https://noclip.website , so I get some of the performance benefits today, under ANGLE, but WebGPU has these best-practices baked in, so everyone will see an increase.

[0] https://github.com/magcius/noclip.website/blob/master/src/gf...