I think it's really interesting that Shinobu Yagawa and Tsuneki Ikeda are so instrumental to the development of bullet hell shmups, and yet their games are, in many ways, almost completely opposite each other in what they expect from the player.
It's also really funny because Dodonpachi Daifukkatsu Black Label is an Ikeda game that Yagawa got to take a pickaxe to, which is why from a design perspective it's one of the funniest games Cave has ever made.
mastering many Ikeda shmups is almost entirely about executing a perfect run of a largely fixed and incredibly tight path, and growing out of tools that are largely only for correcting mistakes (read: bombs)
mastering many Yagawa shmups is about using every tool in your arsenal, frequently in nonstandard ways, and rolling with the punches of a very dynamic system with lots of variance through both random and non-random elements
it's interesting how those two ended up making games at the same company