Anyway, it looks like you pretty easily recognized some of the things that make the Saturn version of Donpachi less than arcade perfect. It's still the only physical version of the game I personally own, though, and I'm a weirdo freak who actually likes Donpachi more than Dodonpachi (Daioujou Black Label still the GOAT, though).
This caught me off guard a little bit. Were you using a separate button to get rapid fire? I only ask, because generally it's just the fire button, and the bomb button, where if you tap the fire button you get regular bullets, and holding the button down turns it into a big fuck-off laser. Also, the laser ends up being so important for scoring in Donpachi games that I tend to kind of think of it as the main form of fire and just have the fire button held down 90% of the time. (It gets me killed a lot because of the slower speed when firing MAH LAZAR.)