I can attest that getting in the door with CitiBank using their "backed cards" such as Home Depot will have zero effect (at least for me) on getting one of their branded cards - other than having an overall credit history. I have been approved for many Citi-backed cards with various credit limits from fairly small ($1k) to fairly large ($25k - HD). All but one of these I've ended up closing due to high APR and better options. Citi will NOT approve me for a primary Citi-branded card, end of story period. I have no idea why, but they will approve the DW and since the only one "we" wanted was the Costco-Visa, we have it. Even with a perfect history of using an HD $25k CL card, Citi won't issue me a branded card - go figure.
As far as high apr HD and Lowes cards, I have both and find them to be very valuable for extended 0% or low apr financing (or) 5% back instantly. I always PIF for any everyday purchases, but I regularly use 6 months 0% offers and have used several times low interest "project" offers - most notably a $10k new roof for 84 months at 2.99% which I paid off in about 30 months.
IMO for a homeowner, Lowes and HD "store" accounts are very useful if managed correctly.
