It('s supposed to) depend on your class:
Smugglers want Evasion because they get 150%. Once they hit the 50% cap, other stats should be prioritized. I go for Shields.
Tech Specialists want Shields because their Recovery ability restores based on Max Shields (& Level & Intelligence). I've made it to Zheng Shi in Atma Armor, even on a Drone Tech. The 20% bonus to Armor Defense is useless. I'm not even sure why they have it (you really don't want to take Health damage). You could also build for Evasion, especially later, because Rapid Recharge (recently got nerfed) restores Shields every round you don't take damage. Stun weapons are also really good for this.
Mercenaries want Bonus HP & Defense because their Recovery ability restores 1/2 Health. I usually put a lot of emphasis on Shields, simply because they come back after every fight. 'Tough' and 'Tough 2' also apply to Shields.
Ideally, you'd match Armor resistances to incoming damage types, but I don't usually bother, except for 'Airtight' negating certain Lust attacks.
