Corrupt Arcana vs Arcane Preparation

[Fates]

The Corrupt Arcana feat (Heroes of Horror) allows a spontaneous caster to prepare corrupt spells in their spell slots, provided they have some sort of spellbook, scroll, etc containing the spells needed. However, the Arcane Preparation feat (Complete Arcane) allows a spontaneous caster to prepare spells they know, usually for the purpose of quicken spell, etc.

My question is, does Arcane Preparation do it better? By RAW, it seems allow the caster to prepare corrupt spells just as well, but then I might be missing out on something.

[Scow2]

Corrupt Arcana does it better, because then you don't need to spend a spell known on the Corrupt spell - which you can't do anyway. You can't learn Corrupt spells as a spont. caster (To my knowledge), anyway, so Arcane Preparation doesn't help

[Fates]

Corrupt Arcana does it better, because then you don't need to spend a spell known on the Corrupt spell - which you can't do anyway. You can't learn Corrupt spells as a spont. caster (To my knowledge), anyway, so Arcane Preparation doesn't help

Ah, right, silly me. You don't actually know the corrupt spells, so Arcane Preparation doesn't work. Makes sense, thanks a lot.