What is more important: luck or fighting spirit?

2 AmberSoler
Did you check? I checked and even wrote how long it took.

Yeah... :) Even with the Spirit of Despair, a morale bonus still occurs... This means that the negative effect is NOT neutralized. What else is there to check? And you don't need to hover the cursor over the monsters; just wait for the first morale bonus in battle – check it again on five units from different castles. You'll be convinced very quickly...

Added after 6 minutes

But, to get to the point, I'm using a non-scientific trial-and-error method because I consider both skills equally valuable and equally useful – it's always nice to get an extra turn or deal double damage.

However, it's worth noting that a double turn when morale occurs allows a unit to deal full damage, while the "double damage" from luck actually only doubles a small part of the damage (the base damage).

That is, if a unit's base damage is, say, 10 HP (shown in the unit's stats), and the actual damage is, for example, 50 HP, then when morale occurs, the unit will deal another 50, resulting in a total of 100 HP in one round of battle. But when luck occurs, the damage will only increase by the base amount and will be only 50 + 10 = 60 HP. A significant difference in favor of morale when comparing... :)