Mass-effect – the base duration for Defense Drone

As far as game saves specifically they are locally stored only. I've seen nothing to indicate cross-platform character usage.

Other than the fact that drones can move and turrets don't as Raven pointed out, here are the other major differences:

• The base drone damage is higher 40 to 25 and the drone gets more potential damage/shield upgrades.
• The turret can potentially get an ammo effect (AP or cryo) and a flamethrower (high close up dps)
• The drone can get an explosive effect when it dies and chain lightning (stun multiple targets)

The combat drone is offensively oriented and seems to be typically way better at distracting large targets than the turret as it can, and will, move in close and start zapping away. The turret is a lot more defensively oriented, designed to hold one spot on the battlefield or protect your flanks, etc.