Wondering how google's angle (GLES through D3D) fares in this respect? https://code.google.com/p/angleproject/
You can then run the WebGl Conformance Tests[1]. I found that my integrated Intel did better in ANGLE and Nvidia card did better with native drivers. Epic Citadel WebGL also slightly faster with native Nvidia.
[1] https://www.khronos.org/registry/webgl/sdk/tests/webgl-confo...