I'll try to make this quick:
I was once debating what's the point of most of other "Fighter" skills when Bold Fighter (aka Bullshit Fighter) has no HP drawback, and you're completely nullifying the lack of Spd and avoiding a double yourself (assuming you kill on your phase).
Turns out, Armour mobility is sort of the drawback. You're kind of always depending on either an Armour team or an Armoured buddy with Armour March, which really takes the flexibility in teams in other non-Arena areas (i.e when you have a bonus Armoured unit for Trials).
Unless you're something Firesweep Effie or Jakob with Boots but fuck them.
Vengeful Fighter is also better with DC, since you're basically all Enemy Phase by then. Even if QR is a thing, the free Seal slot allows for stuff like Distant/Close Def for far more longetivity of both, skill and thereby your own unit.
I actually highly consider giving this kind of set to Christmas Lissa.
Disadvantages of bold fighter:
- dead B-slot during enemy phase, which is pretty significant if your spd sucks. Unless you have guard on your weapon, specials are incoming.
- with some exceptions, no desperation. Can be significant for someone like H.Henry who might not survive two or three hits.
- cost / availability. It's much more available than before, but wary fighter will be more available for a long time from now.
- less potent than special fighter if you have other ways to double. On player phase, one less special charge; on enemy phase special fighter is better in multiple ways
- null follow-up is a thing, and wary fighter is a thing, and Thunder Armads is a thing, and breakers are in the meta.
- as you pointed out, you're expending a B-slot on a unit with mobility issues to focus them on player phase.
Advantages of bold fighter:
- probably still pretty high win rate
- bonus special charge independent of any stat comparison. Can be important for galeforce
- potentially cracks wary fighter, breakers, etc.
- doubles no matter how much IS powercreeps spd
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