The interest rate on the credit card is roughly the same as most other credit cards; the APR is inflated by the annual charge, which is 1/3 that of the Plat. Pay it off monthly, which you would have to do on the Plat anyway, and there is no interest of course so it is cheaper to run than the Plat charge card.

The BA PP does have a better Avios earning rate (1.5 per £ on normal purchase and 3 per £ on BA spend), plus the 2-4-1 at £10,000 spend, effectively doubling the earning rate.