Cherry Brandy is completely different from Kirsh. Cherry brandy is red and thick'ish - normally bottled at between say 15 - 25% and Kirsh is distilled and generally pretty clear and spirit in character.
Appreciate your interest but I guess as you don't know the difference you may not be able to help .... thanks anyway.
@ UK1 - perhaps it was not your intention, but it is likely that most people are interpreting this post in general and the bolded portion in particular as pedantic and rude.
But to answer your original question, it's really about what you want to do with this Black Foresty Sachertorte. Are you after a boozy flavor? Go with Kirschwasser. If you want to punch up the cherry flavor, go with a quality cherry brandy.