Brave Weapons Because…?

I don`t exactly remember what Effie`s atk stat is, but if she had a 16MT weapon with 40 atk, she would do one attack for 56, (obviously not counting foes defense), But a brave weapon with 11 might (i think), she would do two attacks for 51 damage. That can one round KO a lot of units...

It's not really "making a big attack into two little ones".

I had a scenario in mind where Effie is a blacksmith and wanted to explain it like forging a weapon, but that's to complicated.

Let's say your Effie deals 30 damage (it's only for this scenario, I know that she deals more damage) with a normal attack with, I dunno, maybe Berkuts Lance + and has 54 Attack.

With a Brave Lance + on you have 48 Attack but attack 2 times dealing about 20-24 damage (don't know the calculation, just guessing) and deals effectively 40-45 damage with that double.

So even if you lose Mt with the Brave Lance against that Berukts Lance it does effectively more damage since you attack 2 times instead of only once.

*If this is wrong please correct me, since I'm not really into calculating the exact difference between the damage output. Only speculating.*

A brave weapon does indeed have a lot lower atk than a normal lance.
But remember, a unit has their own atk stat, unaffected by the weapon.
So in practice the atk is like 2x 75% of a normal attack, making it very useful on units with high base atk.
But it does hurt if a unit doesn't have at least 35 base atk. Since 2x0=0

Brave weapons are better against units that don't have sky high defenses, but also have decent enough defenses that one attack wouldn't KO.

Even if the weapon's MT was halved(Which it's not, unless you compare it to Prf weapons... which any unit that comes with a Brave weapon wouldn't have) that doesn't mean your own attack is halved. You get 8 less Attack than your usual Prf weapon, but you attack twice at the cost of 5 speed (Usually).

Going up against a unit with 30 defense while you have 60 with a Prf, you'd do 30 damage in one shot. With a Brave, you'd have 52 and would immediately do two shots of 22 damage, totaling out to 44. You also get the added bonus of an accelerated special, but that works both ways, so you better make sure your target is dead.

Brave Weapons For Me Are Hype And Situational:

Situational:There Are People Who Can Hit 40+ Spd Without Buffing While Using A Brave Sword/Lance/Axe/Bow/Whatever,And Using Them With Desperation Is Actually Useful.For Example,A +Spd Sumia(Like Mine) With A Set Up She Reaches 43 Spd Whit A Brave Lance.While Bows Uses A Different Tactics,Using Desperation And Double Savage Blow.Armors Can Easily Run Galeforce With A Bold Fighter Quickened Impulse Brave Lance.Effie In My Opinion Is One Of The Best Candidate For It(A +10 Effie Swepped My Entire Team In AA).Sure,They Are Weaker,But Doing,I Don't Know, 20x8(Total 160 Damage) Is Actually Good.

Hype:Many People Uses For Slow Units The "Brashperation" Setup.Maybe You Already Know About It,But I Will Explain It Either:
Brashperation Allows A Unit To Do Damagex4,Not Counting The SPD Difference Between Foes.If You Lack Of Bold Fighter,You Can Go With That Setup.I Actually Remember Using A Brashperation Effie Paired With A Fury 6 Eldigan,And Effie ORKO Everyone When She Was In Range.

"Well,I Know I Haven't Answered 'Completely' Your Question,But I Wanted To Share My Opinion On Brave Weapons"

You really need to run a simulator if math doesnt come naturally.

Brave weapon 8Mt?, lets compare it to something with 16 Mt.

You have a 40 Atk stat which means you do 48 damage verses 56. What will do more damage, 48 x2 or 56? Unless this person you are fighting has more than 40 defense the first one will do more damage. And even that will charge your special faster.

https://arcticsilverfox.com/feh_sim/

Others have already stated why Brave Weapons are so powerful on player phase. I just like to add that the penalty that Brave Weapons induce (-5 speed) doesn't really matter for Effie as her speed is unsalvageable anyway. Another reason why Brave Lance is such a good fit for her. And with Bold Fighter, she can reliably quad and proc specials.

However, Slaying Lance, Slaying Spear and Berkut's Lance are all very good on her. Slaying Lance makes her very self reliant in a Galeforce set-up, for example. Slaying Spear makes her a danger to every armored unit, Greens included. Berkut's Lance, along with, say, a +res nature or refine, makes her incredibly bulky on both side of the spectrum.

All in all, you should first choose the role or roles you want her to fulfill, and base the weapon selection off of that.

I only use effie with brave lance for Abyssal maps and grand conquest.
If you give her BF she can attack 4 times, then proc galeforce and attack again or return to safety to your squad.
For other modes like arena, berkut lance and slaying spear are better options.