Essentially there are four types of foundies.
"Wild or caught" horses - these will only be one of three breeds - Arab, Belgian or Prezwalski. They have a better range of colours than the sponsor bought foundies, but not so good as the goodie page foundies, and they are completely random as to gender, colour and breed, and you get 6 free with each sponsor renewal.
"Veteran Rewards" - You get the option of a different breed every time you upgrade your account - Sea Horses for one year, Night Horses for two years, War Horses for three years, Ethereal Horses for four years and Alicorns for five years. These horses will only be the default colour for their breed - Heart of the Ocean, Night, Pure Black, Translucent and Pure White. You will always get a breeding pair of these. You can't buy foundies of these horses any other way.
"Sponsor bought" - These cost 18mil per horse. You have a choice of gender, and a choice of seven common colours - all of which are also player craft-able dyes. You also have a choice of any breed available as foundies.
"Goodie page" - These cost $16 (£8 approx) for one breeding pair. You have the same choice of breeds as the "Sponsor bought" foundies. These come in a much wider range of colours, which are not craft-able. (I recently got Chocolate Bay; Rum Chestnut; Burnt Chestnut; Orange Buckskin; and Gold Cream - but that's only a few of the colours.)
The stats should be roughly even no matter how you buy them. There's just variation between the individual horses, as usual.
