i think there should be an option for people who are neither of them :P i just do whatever is needed, and when looking at years ago when i was active in eggwars, i was just the "leader" of our group and switched between everything. always 1 defender who got tanky, at least 1 attacker and i'd get diamonds and stuff from mid most of the time. just farming, but nothing weird like a huge castle
okey little edit on what i said, we DID make a huge castle once x3 but that was more as a joke, the other team was actual camping anyways. what else are you supposed to do with all that potential obsidian? build defence for your egg? pfffff, no! a castle made of obsidian and stuff is way cooler!