in wvw, players can buy blueprints from order representives based on the order they joined. the seige weapons and hireable guards will have different tactical pros and cons.
for example: the durmand priory can build acidic rams, arcane deployable cannons and hire elementles. the vigil could have arrow towers, battle suits and hire a champion and the order of whispers can have smoke bomb catapults, traps and hire spies.
this may be a little to fantasy but those are just examples.