#3/13 = B/B (balanced breed, lowest stats overall)
#4/14 = P/P (power breed)
#5/15 = S/S (speed breed)
#6/16 = H/H (health breed)
#7/17 = H/P (stats split between health and power)
#8/18 = P/S (stats split between speed and power)
#9/19 = H/S (stats split between health and speed)
#10/20 = P/B (extra stats in power, health and speed are balanced)
#11/21 = S/B (extra stats in speed, health and power are balanced)
#12/22 = H/B (extra stats in health, speed and power are balanced)
Different breeds have different amounts of points and how those points are allocated varies between breeds. Speed breeds (S/S) put all their points in speed, plus they ahve more overall points making them very fast, Balanced breeds have the lowest amount of points but they are spread equally between power, health, and speed, etc etc. Here's Warla's chart to explain further: http://schaffhauser.me/Warcraft#BattlePetInfo
The best breeds depend on pet family and their moveset, esp their moveset. And of course not all pets come in all breeds so you pick the best available. Breed matters more to some pets than others, IMO, and a good pet with a good moveset is a good pet regardless of breed, usually. Pretty much anything you can say in pet battling always has an exception though.
Oh, and breeds 3-12 are males while 13-22 are females.
Here's the addon: http://www.curse.com/addons/wow/battle_pet_breedid