Generally i would think moss would be a better ground cover for toads because moss provides moisture and humidity recreating naturalistic microclimates while leaves look asthetically pleasing, they dont do much except but make great cover for the microfauna such as springtails, whenever using moss, make sure to use moss you use is no an impaction risk (Zoo med frog moss), i know that frogs can get impacted on anything but be careful about the leaves and moss