FatMidget, since you mentioned you were new to the game, I will avoid the flaming and try to explain it to you.
There's a situation for each approach. In certain situations wielding two one-handed weapons instead of one two-handed weapon might be better. Usually dual-wielding means a steady and sustainable damage output. Two-handers hit slow, but hard. Maximum damage on two-handed weapons is usually much higher than that of one-handed weapons. So when a two-handed weapon crits, it really hurts. This makes the two-handed weapons useful for PvP where it's all about killing your opponent fast.
While dual-wielding might be just as fast as the two-hander, the two-hander might crit and chop off a lot of health from the opponent, maybe even enough to kill him instantly. The same is nigh impossible to do with a dual-wield build.
Now, attacks are divided into three groups in this game.
1.) On next swing.
2.) Casting time.
3.) Instant.
Heroic Strike, the basic attack of the Warrior, is a 'on next swing' attack. It adds some extra power to the next swing you do with your weapon. If you have a weapon with an attack speed of 2.4 seconds, Heroic Strike will hit every 2.4 seconds, provided you keep using it.
Slam, another core ability of the Warrior, has a casting time. You activate the attack and it counts down from 1.5 seconds (correct me if I'm wrong here) and then your character performs the attack. Usually such attacks puts the weapon's normal swing time on pause, but if you time it right, you can get off a Slam just before your weapon is about to swing again, thus doing two attacks at the same time (again, correct me if I'm wrong - I don't remember if Slam pauses the auto-attack).
Mortal Strike, a talent in the Arms talent tree, is an instant attack. You press the button and the attack is performed immediately. It doesn't reset the swing time of your weapon either, so with practice you can get off an instant attack along with an auto-attack at the same time.
Since the Warrior has so many instant attacks at his disposal, using a bigger weapon is usually an advantage. The higher your weapon's maximum damage is, the more damage all attacks will do. With a lot of instant attacks at your disposal you can do a lot of damage quickly.
It's the difference between doing 2,500 or 1,200 damage with a Mortal Strike crit. If your opponent has 2,500 health left, but is in the process of healing himself, the big weapon will kill him before he can heal himself, but the one-handed weapon will only chop off half his health, allowing him to complete the heal before you can finish it.
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Please "talk up" if your comprehension white-shifts. I will use simple-happy language-words to help you understand.