The fight sticks only go in eight discrete directions, the cardinal and ordinal points of the compass.
The WASD keys do the same thing for PC gaming.
An UltraStik is an analog stick and can go in any direction, hence the name UltraStik 360. It can also be programmed, using their UltraMap program, to act like a fight stick, but mostly it is used as analog stick.
To get multiple speeds out of WASD keys, the CTRL key is often used for slow and the SHIFT key is used for fast, to get three speeds, but you don't need that with an analog stick.