Uh... What are you even trying to ask? Doesn't matter the breed, or even species - ALL of the currently living equines that I'm aware of share the characteristic that when they ejaculate, the glans flares. Depending on an individual's physical size, it will likely be comparably sized to the critter. From a mini with 16 or 18 inches of dick as thick as my wrist, to the biggest drafts with 2+ feet of dong as thick as a salami, or maybe a big zuchini. The flare most often happens as deep inside whatever he's breeding as he can get it, but at "fall-out" time, it's very often visible, and might be as big as a fist for the minis, and as wide as a dinner plate for the heavies like percheron, clydesdale, shire, etc., including vanners. "Paint" is a color-pattern-based "vanity breed registry", not a breed. ANYTHING from minis (where it's particularly prized by some) to mustangs to you-name-it can have a paint pattern that would give it an excuse to be called a "Paint Horse". Appaloosa is likewise a pattern, but so well defined and specific that they've formed a registry based on it. Unlike Paint, it IS so well-defined and specific that they're considered an actual breed in and of themselves. Donkeys, Zebras, Asses, Onagers, and even the (usually) sterile mules that crossing any of them produces with each other or Equus caballus ("regular horses") also flare the same way. Which one is going to flare to what size is only "sort of" predictable, usually more or less in proportion to body size. Individual variation makes trying to pick "which one will have the biggest/smallest/thickest/longest/shortest/fattest/whateverest" dick an exercise in futility.