5Atk 3All or 7 atk scrolls on fafnir weapon?

This is all approximate, since I no longer play my Kaiser, nor do I have it equipped, I had some 400 ATT with the sword, let's say 396 with a theoretically sword with all +3/+5 20s, like, 3.5k STR, with about 200% STR, unknown, but probably 0, % ATT. If we find the STR:ATT ratio, here we'd have somewhere around ~1167 STR vs 396 ATT, or roughly 3 STR being the equivalent of 1 atk, then the 4atk gain from the +7 20 scroll is equivalent to 12 STR, while the +6 STR would boost my STR by 18 with the 200% STR. This was my logical fallacy.

If we work purely on calculating using the damage range formula, then, we have, approximately:
1.32 * (4 * 3500) * 400/100 vs 1.32 * (4 * 3518) * 396/100 which is 73920 vs 73557, which is clearly advantageous towards the +7 20% scrolls.