What is more important: luck or fighting spirit?

Luck is better, in my opinion. For example:
A) We have a well-developed Battle Defense (BD): our troops attack, and they are repelled. Then they attack again, and are not repelled. Unless, of course, they are griffins. ;)
B) We have well-developed luck: our troops hit, deal more damage, => the counterattack will be smaller, which is already very good. And if they attack griffins, they won't even get a second chance to counterattack. ;)