The question of which credit card offers best value has been asked many times and will no doubt continue to be asked.
The only fair and consistent way of comparing is to use different cards at the same merchant at the same time, hoping that they will be processed and charged at the same time and appear on statements at the same time. This avoids daily rate variations. This is usually difficult to arrange for one person.
Having said that, I have regularly used my Nationwide Visa and AmEx (and occasionally other) cards in the same location outside the UK if not at the same merchant. Without fail, the Nationwide transactions are cheaper, usually by around 2.75%. At one time, Nationwide offered reasonable cashback on all purchases (1% I think), but this is now only 0.25% and only on UK purchases.
As to whether lower prices with no miles or higher prices with miles are better, this is clearly an individual decision. FWIW, my UK spending on fuel and supermarkets goes on my GE Money MasterCard, earning 3% cashback up to £5,000 p.a. (and 0.5% on other expenditure). For me, this is better than earning miles.
My business expenditure goes mainly to AmEx cards of different persuasions, and the fallback card is the bmi MasterCard.
Ain't life complicated?
