[Taqwus]

Not a whole lot. Stealth/Scattering Armor only provide cloaking in the Active/Passive EM modes, so a ship hidden only by one of those (not full cloaking device, nor nebula) should be visible to even the lowest levels of the other three (gravitic, psychic, temporal). But the cloaking devices, mine innate cloaking ability, and nebula cloaking are all equally effective in all five types IIRC. So beyond the two armor types, there's just device and research cost.

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-- The thing that goes bump in the night