Size and weight
A wider or heavier gate needs a stronger operator and sturdier hardware. Two gates of the same width can still need different motors if one is solid steel and the other is light aluminium.
How often it is used
A home gate opens a few times a day. A community entrance may open hundreds of times. Operators are built for different duty levels, so heavy use usually means a more robust unit.
Controls and safety
Remotes, a phone app, RFID cards, keypads and camera-based access each need compatible controllers. Safety devices such as photocells and safety edges are part of a proper job and are worth including.
Site works
Civil work, new foundations, electrical cabling and gate fabrication change the scope. A site visit shows what is needed, so the quote is one clear number rather than a guess.