Heavy drones are slow and vulnerable. DPS looks tempting, but they are gone soon if you attack a whole bunch of NPCs, also because they are slow on their way back to your ship.
Some recommend sentry drones for ratting.
4x Augmented Heavy might be better than 2x Gecko, especially when you only call the one back that comes under attack and let the other 3 fight. Remember, the drones do not make any damage while on their way back, so while calling back a Gecko you lose 50% of your drone dps, while recalling a Berserker you only lose 1/4th. Also Augmented Berserkers are pretty fast for a heavy drone (faster than a Gecko, track a bit better than a Gecko) and a lot cheaper, while doing a bit less total DPS. Against opponents weak to Explo/Kin they might outperform Geckos who deal 25% per damage type.