Randomized initiative is a hold-over from wargaming that I’ve never particularly cottoned to. Originally D&D didn’t even have it. Turn order wasn’t even specified, leaving it up to the referee to figure out. I’m sure Chainmail had rules, but the d20 vs. AC “alternate” system that was in the books which everybody actually used made no mention of it. Basic D&D officially had turn order alternating between the two sides, players and NPCs. In that context it made perfect sense to roll at the beginning of combat to see who went first. For some reason, though (at least by the time of the Mentzer Basic D&D) the rules called for rolling each round, which had the bizarre property that a side might go twice in a row. Unfortunately, strict alternation by sides is a) very “gamey” feeling, b) can convey a huge advantage to the side that goes first, or the side that goes twice in a row, leading to a lot of combats where one side or the other doesn’t even get a chance to react before being defeated, and c) doesn’t leave much room for having one character being noticeably faster than another (though Zombies did always lose initiative, no roll needed). Individual initiative feels more natural, and gives a much more fluid feel to combat resolution, allowing characters to react to changing battlefield conditions–perhaps unrealistically so, but a much better fit for adventure fiction. Oddly, to my mind, many systems with individual initiative rules nevertheless include a large, even overwhelming, random component. That puzzles me because it still feels very much like a game, and it inevitably leads to layers of extra complication to try to shoehorn character ability back in…plus slowing play down with extra die rolls and modifiers to arrive at a result that is arguably much less true to either reality or genre fiction. I grudgingly use Savage Worlds’ random initiative system when I run that, in part because the Edges that represent one character being quicker are fairly substantial, but in all my own games turn order goes strictly by the character’s speed. Usually that’s Dex or the equivalent. I’ve toyed with using Int (to represent “quick thinking”) and even incorporated it into a game once…but nobody who’s spent much time around my friend Russell–who is quite literally one of the smartest people on the planet–can take the notion of a strong correlation between brains and fast reaction time seriously. It’s probably better to represent quick thinking as taking some specific advantage (along the lines of and Edge or Feat) regardless of attributes.