Salsa On 1 is the best choice for the beginner to start with, because it is the easiest to learn and the most authentic.
5 The Most popular salsa Dance styles
Learn Salsa dance in 5 private lessons
Salsa On 1
L.A. (Los Angeles) Salsa is also "On 1". Came from 80s, absorbed some western elements including Ballet aerial works and lifts and regarded by Latin-Americans as a theatrical ballet for the western world middle-class.
Salsa "On 2" is a New York Salsa. Dancers skip the 1st bit and make 1st step on the 2nd beat. You need to have years for music and feel the rhythm to hear that 2nd beat to start most Salsa steps. Not the best choice for the beginner.
Cali style is Colombian and has an emphasis on speedy complicated foot work. See Cali dancers at the Cali Festival here and here.
Salsa On 2
Cali Style Salsa
Salsa Dance Nights
Ballroom Mambo is a formal refined style "On 2" with the emphesis on refined technique and elegant lines of arms, legs and body vs more relax easy look of "street" Salsa on 1.