saddestrobots , 
(this hot take brought to you by a decade worth of various people's unsatisfying attempts to make a system for armor/weapons in Fate)
two easy ways to avoid zero-sum / everyone-beeline-for-the-biggest number weapons & armor rules in your lightweight rpg:
makes accessing the big thing legitimately costly — in money, training, social resources, and "suiting up" effort
make the bonuses contextual or rock-paper-scissors type shit