No need to edition war.
I still think it comes down to how magic works.
My trouble with it being possible to memorise a spell in five minutes is that it's not restrictive enough to prevent anyone doing it. See: minor spells - not just spellcasters get them because they are trivial.
The way in which the Wizard uses magic says a lot about the nature of magic in the game. It doesn't have to be the only kind of magic, but I think most people agree that the most powerful, the most game-changing and reality-warping spells end up in the hand of the mage. Preparing spells daily leads to a Wizard that justifies his intelligence score - he has to have a powerful mind to contain these spells, and it takes careful thought to prepare them.
Because a spell component of the spell is the spell itself. That is why spell scrolls can only be used once. It's apart of the lore of D&D, always has been until 4e ****** it up.
1: I think you're using AD&D not 3e lore there. But like so much of 3.0 it changed the lore in a plausibly deniable manner.
2: You're missing the point. Why can't you have small spells that only take five minutes to prepare? And that don't create quite so big holes in the caster's brain? This isn't about spells not erasing themselves. It's about small spells being easy to re-prepare.
Someone mentioned a system that had Simple, Complex and Exotic spells IIRC. Complex spells could require a day's rest, and Simple spells need less.
At-will spells might be Very Simple spell runes and you can juggle a number of these simple spell runes around in your mind's eye at a time.
The difficulty of the spell is based on its level, after all. Why is random level 3 spell so much easier to memorize and cast than the rest of the level 3 spells? Just because it is deemed arbitrarily weaker than the other level 3 spells? If it is weaker than other level 3 spells, maybe it shouldn't be a level 3 spell or increased in power so it is a useful level 3 spell.