That’s hard to answer.
In order to see how good the factions are at waging war at each other, we would have to create a situation where Thrall or Vol’Jin would be in command Vs the most capable leader the Alliance had in WoW, which was Varian.
On the other situations the narrative is tide to the good Vs bad, where good wins on the end and forgives the other faction, because that’s what good guys do.
We wouldn’t had none of that, if they were capable of writing a conflict in which both factions are justified.
In example: border conflict.
Each time the Alliance and the Horde are at each other throats is when the Horde is lead by a evil Warchief.
- We have evil Warchief having military victories such as Theramore or Teldrassil.
Through tactical tactical advantage, while portraying the Alliance as totally useless to say the least.
Varian sent his best Generals to Theramore, everything was set for a huge Horde bloodbath, Garrosh came with a plot weapon out if no where.
Mana Bomb and Theramore is no more.
As mentioned before:
The Night Elves send their best troops to Silithus and they get caught with a surprise attack, from a place they should already know by now.
Everyone forgot to bring blight masks in Undercity, even though they know Forsaken use it.
Than we have characters such as Vol’Jin, Kelantir, Farley, Baine showing outrage for such a dishonourable act, regarding Garrosh.
Or in the most recent case Saurfang and Baine, regarding Sylvanas.
The Alliance retaliates.
But they are never allowed to cross the line, since their hands are tied with morality.
The evil Warchief finds himself isolated and his defeat comes afterwards.
How many Alliance weapons were “forgotten” during BfA ?
The vindicar comes to my mind.
In example, we can see Dazar’alor and Teldrassil as two similar cases.
Both involved killing a important target:
Rastakhan and Malfurion.
The Horde fails at killing Malfurion, because Sylvanas trusted Saurfang to do it.
So she burns the Tree with all civilians inside …
The Alliance sends their player characters to kill Rastakhan and they succeed.
That’s the difference, in my opinion.