What is more efficient? Shield or armor tanking?
ral
this depends on the ship you are flying, e.g. most gallente ships prefer armor tanking and have bonuses for it while most caldari ships prefer shield tanking. this can be seen that they either have more shield or armor and also in the slot layout. shield tanking ships have normally more mid-slots while armor tanking ships have more low-slots to fit the modules needed for tanking.

If you ask a more specific question you will get better answers…