The odd thing about armor in Andromeda is this- it has no inherent protection stat. A bullet does the same amount of damage to you whether you're wearing level 1 armor you peeled off a dead Kett, or level 10 armor from the N7 program. What armor does do is give you bonuses. Some do, admittedly, give you damage resistance bonuses, but they're just as likely to give you weapon accuracy, or biotic damage bonuses, or extra ammo and shields.
One thing you can count on is that each type of armor always gives the same bonus. For example, Kett armor always give s Combat Power Damage Bonus and a Weapon Damage bonus. The higher the level of the armor, the greater the bonus becomes.
The chestpiece a of a given set often has a special bonus that none of the other pieces have, and can take a mod, allowing you to customize it somewhat.
Pick your armor bonuses to suit your playstyle, but it's hard to go wrong with the XP bonus provided by Initiative and the bonus pre-order Deep Explorer armor. Few bonuses are as helpful as an extra few levels under your belt.
Armor Bonus Types:
Angaran Armor: Tech Power Damage, Tech Duration & Max Shields. Chestpieces adds Tech Construct Damage.
Deep Explorer Armor: Equips as a set, cannot be leveled, modded, or improved. Encounter XP & Weapon Damage bonus.
Heleus Armor: Power Damage & Weapon Damage bonus. Chestpiece ass Damage Resistance.
Hyperguardian Armor: Health & Shields bonus. Chestpiee adds Melee Damage bonus.
Initiative Armor: Shield Bonus. Chestpiece adds Encounter XP bonus.
Kett Armor: Combat Power Damage, Weapon Damage. Chestpiece increases Power Cell capacity.
Maverick Armor: Headhsot/Weakspot Damage, Spare Ammo. Chestpiece adds Weapon Damage.
N7: Biotic Power Damage and Shields. Chestpiece adds Biotic Recharge.
Pathfinder: Damage Resistance and Weapon Accuracy. Chestpiece adds power Restoration & Defense.
Remnant: Damage Resistance, Health Regeneration, and Shield Regeneration. Chestpiece adds Health & Shield Regen Delay reduction.