I suspected that the FB/MAME comparison my be faulty. Anyway, I also wanted to ask if there is a dedicated thread for bug reporting or if it's preferable for me to make a post for each bug.
It's not a bug more a case of the system your using does not have the power under the hood to emulate these games fully
Irem 92 and 107 games were state of the art at the time, they fire some nifty graphical effects via raster irqlines which
constantly update every other frame or so.
It's these raster updates which can cause the games to have performance issues on lesser hardware, we had the same problems on the
xbox with Irem 92/107 using our FBN port, so we tended to use the older MAME cores as since the games perform better in those cores
it tends to even out the fps.
You can of course disable the raster updates if you know how but that is a whole different story