Which one you prefer?
Dual wielding -2 penalty is a disadvantage. Light armor too! but having the abilities of a second sword is nice!

Don't forget double weapons as a viable option.

It depends on the character you're playing. If you're playing a ranger, well, there's no reason NOT to dual wield.

If you're playing a paladin, the number of feats that are required to dual wield are a pain, especially for a non-human paladin. A long or bastard sword + a shield will give you excellent armor class, or a 2-handed sword if you're more offensively minded. I played primarily with a sword + shield with my paladin, did acceptable damage, and had an armor class of 38 or so.

If you're a fighter, well, it's up to you. You will have enough feats that you can afford to use any fighting style you want. Double weapons are my personal preference when dual-wielding as a fighter, just because they look cool with the heavy armor.

I usually dual weild and I can wear heavy armor. If you play a Ranger you automatically start out with an ambidexterity feat. Not only that but later on at a certain level (I don't remember which) you get Improved Ambidexterity and a Two Weapon fighting feat automatically. If you get all of those feats and a light off weapon (believe me there are plenty of awesome short swords and light weapons in the game) you'll be fine. You probably won't even notice the -2 penalty. I've also noticed that with two weapons not only do you deal more damage but you also strike faster than with a greatsword.