Great question! The list could go on and on...
Hunts or Heinz? Lowe's or Home Depot? PetCo or Petsmart? McDonald's or Burger King? Barnes& Noble or Borders? ooops, never mind, sorry Borders. MaryAnn or Ginger?
The differences are often minuscule and arbitrary.
Sorry I don't have a real answer, but there does seem to be a Pepsi to every Coke, along with people who will defend their preference to the bitter end. Your question made me smile!