MagSafe provides up to 15w, but you have to remember that there are losses with wireless charging that are not present with wired charging. These losses increase as the distance between the wireless charger and phone increases; i.e. cases. 15w is probably, by definition, fast charging (I've never taken the time to look).
As a result of these losses, a wired 15w charger will provide faster charging than a 15w wireless charger will; talking minor differences here. As technology progresses, I expect to see wireless charging increase in performance, but wired charging rates will outpace it--at least until the point we move to a "wireless" world.