Originally Posted by
DieselYVR
You also need to consider exchange rates and other fx fees if you are not using a GBP contactless card. Per transaction charges or poor fx rates could make a significant difference to total cost. If OP is form outside of the UK I would suggest an Oyster card. Put more than enough on it when you buy it and then you will get the balance back when you depart.
I disagree. As you say, it depends if the card charges FX fees or not, what rate is being used etc. Saying all non-UK visitors should use Oyster is a sweeping generalisation.