In pvp you have to burst down an opponent so here is basically fury vs 2h in a nutshell:
Lets say 2h hits for 300
Dual Wield hits 2 times for 150 each (this is exaggerated because off hand hits for much less)
say you have 20% crit for each person
Each person has the same DPS but 2h warrior has much more Burst dmg and more importantly more control over burst.
Most burst dual wield can give out (math is rough)
- (all hits are crits)
2 white hits + whirlwind + overpower = 2*(150+150+150+150+150) = 1500
Probability of this happening (assuming dw have 100% to hit each, which in reality is way off its much lower) : (.2)^5= .00032 or .032%
Burst using 2h:
- 1 white hit + whirlwind + overpower = 2*(300+300+300)= 1800
Probability of this happening : (.2)^2*.7= .028 or 2.8%
Although this is a very rough, example you can still see 2h has more burst potential AND a MUCH higher probability/control over the burst
For fury to apply burst it must crit with a bunch of hits in a row, which is not probable, not even mentioning off hand decreases white hit % and doesnt hit as hard as in the example i drew up. Also fury takes a while to get rolling, you need time to get flurry, enrage, crusader to proc, whereas Arms can apply the burst fairly easily.
Why is burst important in PVP?
If you have a healer healing your DPS target, especially mail you will not have enough burst to take down your target, the healer will just heal through it
The key in dropping PVP targets for a warrior is to save up your bursty attacks then drop them on your target at the same time, this neutralizes the abilities of HoTs, and puts much more pressure on the healer.
The advantage of 2h arms spec is the ability to stack all your burst dmg in a 1-3 second time frame to apply a lot of pressure on your opponents.
The control for the burst comes from the overpower + taste for blood talents which allow you to activate overpower almost at will.
As a 39 warrior you will never have enough dps to slowly wither down your opponents, you need to rely on burst. So a marginal increase in dps will not overide the extra burst you get from a slow 2h weapon. Also your special attacks are modified by the weapon dmg by your weapon, so slower weapon = harder hits = harder speical attacks (whirlwind, overpower)