Stats

Primary Stats

• Bravery means that a soldier may keep his wits even when Morale drops. If you need this, something probably went very very wrong.
• Reactions determine a soldier's ability to shoot first when stumbling upon an enemy, and vice versa. Very important.
• Firing Accuracy should need no explanation. Probaly the most important stat of all.
• Throwing Accuracy the importance of this trait depends on your play style. Most players don't worry too much about it.
• M.C. or Psi Skill: the ability to mind control aliens, once the prereqisite technology is available. Also adds a small bonus to a unit's mental defences.

Reactions and Firing Accuracy are probably the most important stats to look for when hiring new soldiers. Not only are these skills very important in the game, they also require success in order to improve: a bad marksman who never hits will also never gain Experience, while a soldier who has a high Firing Accuracy to begin with will improve on this ability with relative ease. The same is true for reactions.

However, all is not lost if you do have low reactions and firing accuracy. Low accuracy can be fixed by throwing grenades, where the accuracy of the throw is desireable but not as vital.

Low reactions can be exercised by making use of training the soldier in large reaction-fire ambushes. Though higher soldiers will react first, the chance that the soldier will enter a reaction fire queue during any exchange of fire ensures the soldier will obtain a chance at raising reactions even if a shot is not fired.

Secondary Stats

• Time Units determines mostly how far your Soldiers / Aquanauts can advance each turn and how many fixed action costs can be performed. Very helpful. More TUs also reduces initiative loss for each fixed cost action performed.
• Energy or Stamina determines how far your soldiers can run until they run out of breath. Scarcely matters, but the base stats fixes how much stamina is recharged each turn for the rest of the game.
• Health – a soldier with high health may survive an otherwise deadly hit. But as he will be hospitalized for months and probably sacked anyway, this doesn't make much of a difference. The percentage of remaining health influences firing and throwing accuracy.
• Strength, unsurprisingly, determines how much a soldier can carry until she's bogged down by the weight of her gear. Very important as you start to hand out heavy weapons. Also determines how far an object of certain weights can be thrown, a vital aspect of throwing grenades.
• M.C. or Psi Strength: the ability to withstand alien mind control attempts. Will never improve.

Secondary stats are not tied to specific actions and will improve almost automatically. Any weakling will soon enough turn into a Hulk Hogan of sorts.

Combat Stats

• Energy recharge. How much energy the unit will recharge per turn. For X-Com soldiers, this stat is derived from their base energy/stamina and remains fixed for the rest of the game. Aliens and HWPs have particular values assigned to them.
• Fatal Wounds may be incurred when hit. A soldier with fatal wounds will take damage every turn until either: a) she dies, b) the wound is treated, c) or the battle ends.
• Morale changes over the course of a battle, depending (mostly) on how well your team fares. If it drops below 50, the soldier will have to pass a bravery check.