It’s fairly standard now that weapons in D&D do variable damage, but of course the original 1974 D&D (3LBBs) had all attacks doing d6 damage. The spear was the notable exception, able to do 2 or even 3 times normal damage when set against a charge. The Greyhawk supplement ushered in what we now take for granted, variable weapon damage. This was meant to complement the fact that monsters now had “attack routines” and did varying amounts of damage themselves.
The Greyhawk weapons table also added varying damage by size of the opponent, and there was a separate weapon vs. armor table, similar to the one in Chainmail but broken. In any case, the Greyhawk modifications were a pretty large jump in complexity and a move towards more of a simulationist combat model.
Holmes Basic kept the simplicity of d6 damage for all weapons, but tied this together with advanced hit dice and monster variable damage – something Greyhawk explicitly warned against. At least in Holmes’ pre-publication manuscript, monsters kept the d6 hit die from the 3LBBs – it was only later, during editing, that the monster hit die was increased to a d8.
Moldvay/Cook Basic/Expert (B/X) kept the variable monster hit dice and damage, and presented variable weapon damage as an option, but without Greyhawk’s varying damage by opponent size and without the weapon vs. armor table. Moldvay’s simpler variation made it into the B/X clones like Labyrinth Lord and Basic Fantasy RPG (BFRPG). AD&D took the Greyhawk track, including both options.
Now, where does this leave us? In my mind, meaningful player choice is more important than simulating combat. As a player I’d rather have my weapon choice mean something in itself, without resorting to extra tables. Is the weapon two-handed, meaning it might do more damage but prevents the use of a shield? Does the weapon have some other sort of utility outside of combat? Can I use it as both a missile and melee weapon? Cost is rarely a factor outside of character creation, since after the first adventure or two, most characters will be able to afford any of the standard weapons.
For the 3LBBs, if you’re a fighter, the spear is a clear winner. It can be thrown, used as a one-handed stabbing weapon with a shield, set against a charge, and it allows you to attack from the second rank.
For Holmes, as written, the dagger is king – but if you ignore the broken “small weapons get two attacks per round rule”, the spear still wins.
For Moldvay, the sword is the clear winner – it’s one-handed and does d8 damage, whereas two-handed weapons always attack last. Labyrinth Lord (LL) adds a lot of weapon options from AD&D, but quite frankly has a broken weapons table. Many of the choices make no sense (e.g. the two-handed war hammer that does d6 damage, or the two-handed battle axe that Dwarves cannot use).
BFRPG gets points for the most consistent weapons table, having variable damage but also fixing the B/X and especially LL issues with two-handed weapons, the battle axe and the hammer.
Swords & Wizardry Core and Complete also have a nicely consistent weapons table, however, in my opinion, the best compromise between simplicity and consistency is Swords & Wizardry White Box. It keeps the weapon damage variation small (d6 plus or minus 1), while still allowing some meaningful choice. It is my favorite of the bunch.