I doubt there's benchmarks from ye olde days, but are you sure? I thought the first PPC machines managed to outrun 68040 machines, even in emulation. I fully admit my recollection could be wrong there.
But regardless, that entire pre-G3 era was the nadir of the platform. Those were dark days.
It was surprisingly similar to the current ARM transition if I’m remembering correctly. Many, but not all applications actually ran faster even in emulation. But there were certain tasks that didn’t emulate well and the pundits cautioned to wait to upgrade until the tools you used were fully ported.
But regardless, that entire pre-G3 era was the nadir of the platform. Those were dark days.