I am still tied up on people's opinions on "better" which seem to imply objective and always qualities. The prepare and cast (someone's inability to change an imaginary paradigm in a game of, essentially, Let's Pretend is not my liability) system is easy to teach and explain. Playing with a mana point system of any kind (which is really "all the rest") requires a level of sophistication, understanding which spells will scale indefinitely and which won't.
A wizard, cleric, or druid can use a 1st level spell while it's useful, and then prepare a different one after a few levels when it's no longer so good (sleep, color spray, command as examples). A sorcerer is stuck with bad choices made from inexperience. Not so good. For game balance purposes, the wizard can be allowed to add many different spells to his books. The sorcerer is stuck with a few spells known.
I'm not saying that other systems aren't possible, either, or that they aren't usable in D&D. The flexible spell points system and channeling system from Player's Option were outstanding, and were going to get introduced to a game I was playing with--just as soon as I could find one other person who could understand them and use them with the same speed as the current system. (Not to mention how hard it was to find a 2e game at that point in time.)
If I go on strict ease of use, accessibility to new players, and game balance criteria, I'm quite happy with the standard preparation system. Besides, it is more in line with how magic is practiced in real life (although the psionics system is probably more in line with practice of psychic abilities, and it can be quite an exercise in futility to attempt to separate the two into firm camps). I like that.