I fully subscribe to the idea that each of the M6 (and all the mares) have their own flavor of breast milk.

Who can produce (realistic amount here) the fastest, and who can produce the most in general. Hmmmmm....

I agree with Mcgridles1337. In fact, I actually found something that says what flavor would represent your personality.

Rarity: Coffee for an ambitious, driven, and sophisticated person who enjoys the finer things in life.
Rainbow Dash: Vanilla for an impulsive, easily suggestible, and idealistic person.
Fluttershy: Caramel for a warm, caring, and nurturing person who wants to make others feel comfortable and valued.
Twilight: Butter Pecan for a mature, responsible, and hardworking person who values stability.
Applejack: Chocolate Chip for a competent and go-getter person.
Pinkie Pie: Cookies & Cream for a playful, creative, and youthful person with a strong imagination.

always a boon to see my milking machine model used!
especially for titties specifically.