We run Blender's 2.91.2 benchmark tool, using the Classroom scene. Nvidia GPUs are testing using CUDA and OPTIX, while AMD GPUs are tested using OpenCL.
OpenCL rendering times in Blender are fine, but do lag behind the RTX 3060 Ti – with the scene rendering 18% slower with the AMD GPU compared to the GeForce GPU using CUDA. Nvidia cards can call upon OptiX however, making the 3060 Ti almost twice as quick as the 6700 XT.