Brazen Atk/Spd 3 or Fury 3 on Raven

Neither, Life and Death with his Weapon +Eff Refine. Otherwise, Fury because he shines on player phase as a glass cannon. I guess it also depends on what IVs you have and how you want to ideally use him...

I use Fury, and I quite like it. Lets him tank pretty much everything when initiating well enough. Brazen would be well suited to more of a sweeper role with a dancer.

Both viable options. Fury works especially well with a +Def Raven to beef up his defenses more so he's not so frail. Brazen is an excellent choice since he'll almost never be naturally doubled, it's easy to get into the health threshold. Combined with Desperation he can turn into a monster of a sweeper.

I'd personally go with Brazen if I could, but I'm running Fury since I don't have access to a spare W! Robin.

Fury 3, he doesn't need the Brazen buff to pick up kills or doubles on any greens or reds or colorless. It improves his one hit bulk which is important for his first combat versus the hard hitting green armors like W Chrom, M Grima, and LA Hector.

Why are you talking about fury to be more tanky? Fury is used so he can reach safely the desesperation range, and is more optimal +8/+8/-2/-2 than +10/+10/-10/-10 in the case of double L&D.

Brazen ATK/SPD is ok, but you will not be able to reach desesperation range that often

It depends.
1) if you want +3 to all stats (with drawback of 6 dmg after battle) pick fury
2) If you want +7 to atk and spd, but only when Raven is under 80% hp pick brazen atk/spd