> what value does paying with your phone add over an Oyster
Phones and contactless payments actually do the fare-capping calculations slightly differently - if you do a "commute into London, then around London a bunch, then back" travel pattern, it can purchase a virtual central-London travelcard in the middle of the day, and adjust the commute-in payment retroactively. If you want that fare treatment with Oyster then you need to get the travelcard option loaded on it in advance.
Phones and contactless payments actually do the fare-capping calculations slightly differently - if you do a "commute into London, then around London a bunch, then back" travel pattern, it can purchase a virtual central-London travelcard in the middle of the day, and adjust the commute-in payment retroactively. If you want that fare treatment with Oyster then you need to get the travelcard option loaded on it in advance.
> or contactless
modestly better security