I've done great with both warrior and devourer enchants. Rek'sai makes great use of the armor pen and AD from warrior, but not so much the CDR since she already has low cds... with devourer she can stack it insanely fast and her passive attack speed from ult synergizes with on-hits. I've been bouncing between the two, and I see pros using both... but one must be better than the other, right?
Devourer is pretty much always better on auto attackers, because it gives you hybrid damage and scales infinitely
Warrior is mostly for AD casters, which don't benefit much from the AS.
However I have seen Rek'Sai die surprisingly quick in a gank, so Juggernaut may be a good alternative.
Devourer synergizes better with her kit, helps you get your E up quicker and it bounces off the AS boost on her ult, and gives you a better late game provided that you've been stacking it properly.
I personally like Warriors to go as a more bursty Rek, but Devourers is good since she synergizes well with AS and it gives her even more hybrid damage. It honestly comes down to preference though.
