The Martini’s history is as cloudy as a proper Martini is clear. It’s thought to be a later iteration of the Martinez (equal parts gin and sweet vermouth, plus maraschino liqueur and bitters). The original dry Martini was equal parts dry gin / dry vermouth with dash of orange bitters.
How People Like ’Em
Everyone has a preference when it comes to Gin (or Vodka), Vermouth, and in some cases, Olive Brine ratios for their Martini build. Ranging from 50/50 Gin to Vermouth, 2:1 Gin to Vermouth, or “Wet,” to Extra Dry which contains only trace amounts of Vermouth. Then there’s Dirty where a dry Vodka Martini is made slightly savory with a splash of Olive Brine.
Vodka vs. Gin
Vodka will result in a more neutral martini, and it’s usually used for dirty Martinis so the olive brine can really shine. Gin will naturally be a more botanical flavor profile that shines with a little lemon twist.