The bottlenecks are: a) CPU (single core speed); and 2) OpenGL. I noted load times in CMBN (oldest and slowest title) and using MSI Afterburner - looked at the CPU and GPU loads along with GPU MEM utilization both on the old and new systems. Can't find my notes from that time! 😞
I was satisfied once I realized that no scenario was never going stress the GPU. I have what is now considered a rather pedestrian GTX 1660-6GB card.
I'm a recent NVidia convert and can attest that they provide better support for OpenGL which always annoyed me about AMD. AMD has a knack for providing even worse drivers. Wonderful hardware but their drivers are near useless.
Otherwise, any difference will be attributable to single core clock speed of the CPU.
What are your system specs? I'm sure you can get a few others here to run comparables for you.
Some numbers for you... There are other similar posts in the forums if you wish to search.