Archer's arrow explode more widely, but have less concentrated power.
It's like a difference between an explosive and armor-piercing round.
There, I explained it much simpler than I would with the Rank system.
See, that's just wrong, metaphysically.
Archer could just as easily have reinforced the concept of "precision" to the breaking point, and gotten a needlepoint shaped blast for his trouble.
It still wouldn't matter. Its Mystery - its legend, mystic might, historical presence - is insufficient. Biggatons don't really
matter in the Nasuverse beyond a certain point; at high levels of magecraft, it all comes down to concepts.
This shows up in Kara no Kyoukai, too. Araya Souren reinforces his arm with the bone of a hundred-years-dead Buddha. Because its owner was one who ceased to exist without/before dying, the bone is highly resistant to things that try to actualize its death - like Shiki's eyes. In other words, it has high Mystery. But if you hit it with a rock or something, it'd break as easily as any other hundred-year-old bone.
Okay, now for Ranks. Funnily enough, if you say "X has more Y than Z," people will want to know "well
how much more? And is it transitive? If X can beat Y, does that mean it can beat Z too?" (This is particularly important to users of Z, who would like to know in advance if their defenses will be ignored so that they can write their funeral rites.) But quantifying Mystery is kind of difficult - what units would you even use? Bits? Bits would sort of work, but measuring it would be extremely inaccurate, since so much comes down to rock-paper-scissors type concept battles.
So you just give a rough approximation. "A Rank." "C Rank".
And then that Rank system gets co-opted to talk about other things, because it already exists in the literature.