Gun units have weaker damage than melee units, and weaker potential damage than cannon units. However, gun units often make up for this in many different ways; all can equip beam weapons, 3 out of 5 of the (mostly-)dominant gun users gain powerful beam weapons, and 4 out of 5 have anti- weapons. All drones open to guns have very high mobility (except the moth). The mobility bleeds into the most important way it makes up for it: gun-excelling units are rarer than melee units, and only a few gun enemies use gun boosters, so weilding guns presents a method of attack the enemy's weakspot.
There are no true ground-based gun-dominant non-versatile units in the game, not even the centipede with tread, although he is the most potent gun drone in the game. These versatiles are essentially true versatiles. While they have excellent gun stats, guns in general do poor damage. When equipping any weapon but one central one, they also have to lower attack power and defenses quite a bit. They don't gain beam attacks, which they obviously have available in their guns, but the Stag Beetle and Spider do gain great bonuses in their melee weapons, while the Locust and Roach have unique methods of using cannons. They have excellent mobility, and higher than average defenses, but are not good at countering like other melee drones. Stag Beetles are dominantly melee and versatile gun, Locust is dominantly cannon and gun, Roach is dominantly cannon but versatile all, and Spider is versatile everything.
SPIDER"High HP, strong melee & guns" legs, mov 6. macc 130. all-versatile ground unit. no special abilities. weapons: various spider fangs +SPD
Ground-based Gun-Cannon Units Although they have weaker cannon power, they have only have 20 power less than normal cannoneers by the time they reach level 30, they are highly mobile, and are good at guns.
Although it doesn't look like it, the centipede has weaknesses, and that is its low defenses. Centipedes may look scary, but they are very fragile, like a flying unit, except without the speed, in return for melee-level guns. Its most powerful weapon is the most powerful weapon in the game, earned in the second last level of the Badlands with beam type.
CNTPEDE"Anti-air gun unit" tread, mov 5. macc 100. Gun-'versatile' tread unit. guns become anti-air, stats exceed normal balance. weapons: various centipede fangs various effects, side cannons high attack power
Air gun units focus on special effects and mobility (or defense). The butterfly has double heal and beam guns just before in the endgame Badlands, the dragonfly is anti-ground and highest mobility, cicada anti-air and highest mobility, and the moth is anti-ground and high defenses plus gains a powerful anti-ground beam weapon early in the endgame Badlands. The butterfly's speed is the second highest defense stat of all the non-base drones in the game. The dragonfly is slightly good at cannons, and the cicada's defenses are slightly higher, although these are low enough amounts that they don't affect the drone.