Type of spell shouldn't matter at all in a comparison of Affinity to MAB. The math for it is just:
(Y+.3)*X = (X+.5)*Y
Y is staffless affinity. X is staffless MAB.
If Y is 1.3 to start with (using an Atma in Abyssea), then X needs to be less than 217 (+81 MAB over base with traits) for Laev to be better.
If Y is 1 to start with (no Atma, outside Abyssea), then X needs to be less than 167 (+31 MAB over base with traits) for Laev to be better.
If Y is 1.5 to start with (Undying and Beyond in Abyssea), then X needs to be less than 250 (+114 MAB over base with traits) for Laev to be better.
I'm pretty sure that you can hit 31 MAB using level 75 gear and Abyssea Atma make the MAB gap a non-issue, so Affinity staves are better. Heck, Beyond + Ultimate and you're already at 80 of the 81 MAB you need to make an Affinity staff better than Laev.
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