http://shmups.system11.org/viewtopic.php?f=5&t=34497
He recommends MAME over PCBs for practice, though, and save states is one of the best ways to improve your performance quickly:
If your mind is still troubled because you can't help but think you're not
playing the authentic, real thing, then go buy a PCB, but still practice with MAME,
and use the PCB only to perform your high scoring runs.
Saved states will allow you to learn at least 5 times faster by allowing you
to skip those easy first stages, and isolating hard sections that need more
attention. More on that later. For now, just remember it is a really crucial perk.
By all means, avoid PCBs for practicing. They do not have either level
select or saved states and are no good for learning. I cannot stress enough how
important that is. I know the Japanese players who scored in the first Japanese
rankings learned this way, but that's, indeed, only because they didn't have a
choice. Believe me, if they could have used MAME, the MAME users would have
come far on top of the others.
PCBs are also very expensive. If you love PCBs, it's not a bad idea to play
your final scoring runs on PCB though. Just find a way to set up recording
equipment to record off the PCB.