You'll find this armor fairly quickly, and you have no reason NOT to equip it. It has low stat requirements, takes up only the armor slot and no item slots in your inventory, and has no negative points at all! It's like free experience points or stat upgrades with none of the work!

Strength - 2

Great at stopping damage from radiation or toxins. It boosts your Radiation/Toxin resistance by 75. Coupled with a couple of points in Endurance, you can effectively block out any damage you'd normally take from Radiation/Toxins while wearing this.

No Minimum Requirements

The Strongest Armor in the game, it also has the biggest drawback. Powered Armor has a charge that provides the suit with defensive power. This charge can vary from 100-160 depending on your maintenance skill level, if this charge runs out, so too does the defensive power it provides. The charge drops 1 point every 5 seconds so every 10 minutes it's going to need a recharge. This isn't a big problem until you reach the Rickenbacker and recharge stations are harder to come by, but even then there are ways to recharge it, so it is possible to keep your suit powered throughout the entire game. Considering that this armor has the best defensive bonus in the game it's not unreasonable to spend time recharging this when you get the chance. I prefer this over the Heavy Armor because of the lower strength requirement.

Strength - 3

Powered Armor and Standard Armor show up about the same time in the game. Powered Armor gives a +50 defensive bonus, while Standard Armor gives a +30 defensive bonus. Unless you really don't want to worry about the charge of the Powered Armor, I suggest using the Powered Armor instead of the Standard Armor.

Strength - 4

Found fairly late in the game, it offers a +40 defense bonus, but with a requirement of 6 strength. If you have the strength, and don't want to worry about the charge with Powered Armor, this is the way to go. For most people though, the Powered Armor is simply a much better choice.

Strength - 6

Think of this as the Jack-of-all-Trades armor. It confers a 20% defensive bonus, +2 to your PSI ability while draining your psi points, and a 30% radiation/toxin resistance as well. This armor shows up last of all the armors, and the PSI bonus is the only reason to use it. Otherwise, it doesn't have a high enough defense rating when the enemies at this point can kill you in 2-3 hits while wearing it, as opposed to about 3-4 hits with the Powered or Heavy Armors and the BioHazard suit is infinitely more effective at stopping radiation. Factor in the fact that you need a level 3 research rating, and this armor becomes more of an oddity than a truly useful piece of equipment.

Research - 3