So I know most fights being able to cast the debuff as a geo-spell from afar keeps you safe from aoe damage. However some fights it is not necessary. The magic damage formula uses magic attack bonus and magic defense bonus in a mab/mdb ratio. https://www.bg-wiki.com/bg/Magic_Damage
This being the case, when your MAB is greater than the targets MDB, reducing the magic defense further is more effective than raising your MAB. However the reverse is the same as well.
Lets take 600 MAB vs 1000 MDB to exagerate these numbers. Acumen and malaise are both 30 and blaze of glory adds 15. After spells are applied we get:
bog acumen 645/970 = .664 | bog malaise 630/955 = .659
Blaze of glorying the acumen pushes the multiplier closer to 1. Lets reverse and see, 1000 mab vs 600 mdb.
bog acumen 1045/570 = 1.83 | bog malaise 1030/555 = 1.85
Blaze of glory on malaise gives a better multiplier.
So on most things like fodder and apex, geo-malaise would be the best as you can push the de-buff further with job abilities, however is this true for all things like tier 3 and 4 escha NMs?
I'm willing to bet that you generally should stick to geo-malaise but I'm curious if there are fights where geo-acumen would be better.