So go for whichever you want while keeping in mind that the new one is better, I like this choice between an average better mitigation cooldown and a worse but sure mitigation cooldown.
And definitely use the rakata one against stuff like Terminate on the Operations Chief (does 34k if you do not shield/defend). I facepalmed when I used deflection and the hit went through after I told my healers that I'll be fine and wouldn't take damage (around 22-23% chance to get hit but I want my invincible deflection back).
Terminate is a tech attack. Pop Resilience/Dark Shroud and you will take 0 damage just as you intended. :-)