>>725245563
>contacts
rubber membrane (lots of variance in rubber properties and how it's cut)
tactile dome
tactile button
microswitch
>pivot
none
ball
point
convoluted suspension mechanisms
probably other shit
>underside
flat
cross
protruding rectangles
various other shapes that may or may not help with accidental inputs
>external
cross
recessed cross (Sony)
saturn
xbox series circle-cross (several other variations of this style)
xbox elite dish
probably plenty more, it's a component with a lot of internal and external variation
>>725246258
The same reason people like Saturn, you have a surface to press for diagonals but still have a prominent cross to make cardinal directions obvious by feel. There's zero downside to having a full disc.