It makes for fun arguments! The important thing is that the issuer makes no difference in how a card is scored.
There is a difference is scoring for store cards vs bank cards. If you card has the words VISA, Master Card, American Express, or Discover on it, it carries more weight in your scores, regardless of whether it was issued by American Express, Citi, First Premier, or a credit union, or if it has a store name on it (for instance, a Citi Sears Mastercard and a Target VISA both are scored as bank cards.)
Bank cards are also called "majors."
There is an ongoing argument as to whether you need to have a retail (store) or gas card. It is listed as part of the credit mix, but so are consumer finance loans, which are negatives, so I'm not convinced one way or another.
But if all you have are store or gas cards, shoot for a bank card or two. If you have all bank cards, you may or may not "need" a retail/ gas card.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007