I have recorded this video where I tried to reset MAME, the GunSmoke arcade PCB and its FPGA core at the same time. You can see how MAME gets ahead and ahead of the other two as time goes on. I think MAME runs at about 1% faster speed. I am going to try to repeat the comparison after I correct the MAME source code.
-- Source code of all my cores here. My Patreon page here.