> What are typical delays introduced by the emulation layer in MAME compared to > original hardware? Have their been any measurements or blind tests?
You don't need to measure it. On an arcade board the CPU can sit in a loop monitoring your button presses. When you run that in MAME the inputs are only updated every frame.
On seeing you press that button it could change a palette register which will be output instantly. In MAME it's not only had to wait up to a frame to get the input but the frame can only be output once it's fully generated. Which can add up to another frame.
This is before you get into vsync/triple buffer/display driver issues which can add more latencies.