Neither product is massively effective, simply providing some control of the problem, and neither one is any better than the other, as far as I can tell in use. The one I usually recommend for roses is Roseclear Ultra, which is a combined preparation of an insecticide and a fungal treatment (triticonazole), so it deals with aphid infestation too. Can only be applied 4 times in a year, and should not be used while the bees are still working, if the flowers are open.
However, given you've got a hedge, where black spot is much more likely to occur anyway, and it's difficult to get a spray to reach all parts because of the 'thicket' like nature of the growth, then I'd suggest a natural, non harmful treatment for fungal infection, particularly black spot - cow's milk. Mix one part milk to two parts water in a sprayer, and spray till run off. And you can use that mix as often as you like or as necessary, without harming anything in the environment.... link below