The light armour, or "peltast" if you will is the mainstream armour used throughout the majority of Tribes servers. It's uses are many and drawbacks few. You can play light offense, capping the flag or destroying their defenses. Or if you'd like, you can stay back and play light defense, helping out your team; jetting around the base repairing blown up structures and healing your teammates. However, you can always head off and snipe - around your base or pick off the enemy at theirs.
This is something that is entirely unique to the light armour - it's ability to use the sniper rifle; it deals 90% damage to a head shot on light armour. Another unique attribute carried by the light armour is it's ability to pilot the fliers. This being said, having experienced pilots and snipers are your team is essential for winning a match.
However, something that you've always got to keep in mind is that you're at a disadvantage from the moment you change into light armour - YOUR defense. Since light armour is quite maneuverable you had to sacrafice a lot of your armour to provide you with this type of speed. Thus, when you are hit; doesn't matter by what - it HURTS!