Hiya.
...I know I want to say someting...I just can't quite find the right words. Lets just blather on for a bit...
Having played AD&D in one form or another for the last 3+ decades, I have seen (and gone through myself) the "uncertainty" of Vancian magic. In the end though...it works.
Mechanics *do* matter. They matter MUCH more than people like to admit. Example: go to a group of 4e people and tell them you'll run a game set in the current 4e Forgotten Realms setting...using Runequest II rules. How many of those 4e'ers will say "Sure! Lets get started!" without batting an eye? My guess...not many or none. Why? *System Mechanics Matter*
Setting flavours *do* matter. They matter as much as mechanics. The hard-core FR'ers who love the 'new Realms' would jump at the chance to play in a new FR campaign using Runequest II rules. Why? *Setting Flavour Matters*
Taking those back to the idea of Vancian magic...same thing. The flavor of them matter, as do how they are utilized. Some like one more than the other.
IME, the *best* argument for the Vancian system is that it actively encourages the group over the individual by setting it up so that when the wizard does start to run out of spells, it's up to the group to protect/help him. While the wizard has spells, they wait for the wizard to dictate much of the tactics and situations. The wizard shines when he has a spell for something (or has spells), and the fighters shine when the wizard doesn't. Each is responsible for the others safety and success. The BEST thing about 1e AD&D was that it was most definitly a "Group-Oriented" rpg approach. The players were "highly encouraged" to craft characters that worked together, covered eachothers weaknesses, and this translated into play. It also placed a lot of *player* input to succeed, as opposed to *character* input to succeed. In short, 1e made players think creatively, think about group tactics, and yes, think about potential situations. With Vancian magic, the players needed to have their characters do actual 'work' to find out information about what they were going to do, where they were going to do it, and who they were going to do it to. Fighting a necromancer with his horde of undead? Memorize more non-mind affecting spells. Fighting a orc warlord and his minions? Memorize more mind-affecting spells. Infiltrating a bandit lords hillside fort? Memorize reconasance and stealth type spells. With a non-Vancian system...who cares? Just wade in and start casting whatever...no need to plan or think much about it; as long as you have the spell points you're golden.
Overall, I like the Vancian system. It does have some quirks, to be sure, but it definitly feels like it's one more thing to encourage the group over the individual (and, as a DM and player, I'm sick of individual players making stupid characters that are disruptive, incongrous, or outright hostile to other PC's in the group simply because the rules give them the option to make that character...but that's a whole other ball of worms for another thread...).
Besides, it's just as easy to define how and why magic works in any particular way for ANY campaign or game world. I can explain why magic works the Vancian way for a Greyhawk campaign just as easily as I could explain why magic works the mana-point way for a Greyhawk campaign. As someone famous at one point probably said some time in the past: "It's all in the presentation".
^_^
Paul L. Ming