That depends on what do you want to do.
The basic Gate only allows one condition, and can't interact with pipe wire.
Iron gate allows two conditions, and can interact with red pipe wire.
Golden gate allows four conditions, can interact with red and blue pipe wire, and can add item specifiers to conditions.
Diamond gate allows eight conditions, can interact with any pipe wire, and can add item specifiers.
All AND gates will launch all actions only when all the conditions are true.
All OR gates will launch every action if the condition associated with that action is true, regardless of other conditions.
Autarchic gates can activate wooden pipes they are attached to.
Better gates don't give you more conditions to work with, the basic gate can use exactly the same conditions as a diamond gate. The only difference is the number of possible conditions, and the fact that golden and diamond gates can use item specifiers. (i.e. "items in inventory" compared to "five cobblestone in inventory").