Character Statistics
Statistics System Shock 2 has a total of five Stats that define your character's abilities: Strength, Endurance, Psionics, Agility, and Cyber Affinity. Each of these have their own primary and secondary beneifts, and which Stats you choose to increase will have a profound impact on your character's abilities, to a large degree defining how you make your way through the game. Below you'll find a write-up on each of the Stats, including an evaluation of each one's usefulness. Note that while Stats can be naturally increased to 6 using Cyber Modules, the use of Implants and Psi Powers can bring them higher, up to 8 or even 10, though most benefits will max out at around 8.

Governs: Inventory size, melee damage, weapon requirements
Maximum effective value: 8
Evaluation: Strength is, for most characters, the most useful Stat in the entire game. The most obvious benefit comes from the increase to your inventory size, with a new column in the grid added for every point of Strength, meaning you can carry around a few more healing items, some more ammo, a weapon, etc. even with a modest investment. Additionally, many weapons require a medium or even high Strength value to use, including the Assault Rifle, meaning that even if you want to ignore melee weapons, you'll still be almost required to pick up a few points in Strength.

Governs: Hit Points, Radiation and Toxin resistance, Psi burnout damage
Maximum effective value: 8
Evaluation: Despite the obvious advantages of greater health and resilience, the fact is that Endurance is not quite as useful as it sounds. Most characters can easily get away with one or two points due to the abundance of healing items in the game, Toxins and Radiation can be cured with readily-available hypos, and Psi burnout damage is never a serious concern even for a dedicated Psi user. That said, there's nothing like more Hit Points, so if you're finding yourself dying a bit more often than you'd like, some extra Endurance can help. However, it is at best a secondary Stat, and best left until you've maxed out your primary ones, or raised with an EndurBoost(TM) Implant.

Governs: Psi Points, Psi Power damage and duration
Maximum effective value: 10
Evaluation: Psi is, obviously, most useful for characters who are dedicated to using Psi, and increases the damage, duration and overall effectiveness of Psi Powers, as well as your total pool of Psi Points. Psi users should be boosting this along with Strength as early as possible, as the benefits provided are quite high. For non-Psi characters, this can be mostly ignored, though a point or two in here to make Electron Cascade more useful will definitely not hurt, though it's probably more efficient to use Psi Boosters when they become available.

Governs: Movement speed, fall damage, weapon kickback for Standard and Exotic Weapons
Maximum effective value: 8
Evaluation: Agility is probably the least useful Statistic, simply because there are easy ways to raise it or get similar effects without having to spend Cyber Modules - Speed Boosters, Implants, Psychogenic Agility, and so on will all provide noticeable benefits. As for weapon recoil, there's a Psi Power that completely eliminates that problem if you're having trouble. While a couple of extra points won't hurt, you'll simply have too many alternatives and better things to spend your Cyber Modules on most of the time.

Cyber Affinity
Governs: Tech skill difficulty, ICE Node count
Maximum effective value: 8
Evaluation: One of the best secondary Stats to pick up, if not the best, as Tech skills are extremely useful for just about all characters, whether it's Hacking or Maintenance. With a few points in Cyber Affinity, you'll find that your chances of success in Tech tasks are significantly easier, and while it's not necessary to max this Stat out, it's generally worth getting 3 or 4 in it just because of how often Maintenance and Hacking are used.