blastar (./2) :
You are right, the timing is minimally different but generally MAME is the best emulator and very close to the real hardware.
MAME is not perfect (e.g. Raster effects) but if it works in MAME then you can be sure that 99.9% of the time it will work on real hardware - no matter if MVS, AES or NGCD.
The only thing you should keep in mind - ALWAYS use the original bios, the UNIBIOS falsifies some things (e.g. the timing).

Thanks for the tip on the BIOS - I'm running UniBIOS on my NeoSD by default atm...
FWIW my game runs about 1/2 speed on real hardware, as if every 2nd VBLANK is being missed because I'm spending too much time in there. I probably am atm, because my code is very, very sub-optimal to make it easier to debug.
I'm also seeing my emulated foreground tilemap layer shift down 2 lines after a while, which doesn't happen on MAME. Weird, but again, not concerned yet.