Should this be a novel or a game?

I like to come up with stories and game making is one of my outlets. Thing is, sometimes I come up with a story that I think is particularly interesting but would be a nightmare to make into a game. Case in point:

"A modern day witch named Joanna is hunting down a powerful witch named Anastasia who killed her family and forced her into a contract with a dangerous and deadly fire spirit. Will Joanna be able to find and kill Anastasia while also dodging the Magic Council who is hunting HER down for being a vigilante?"

My aim is to make the use of magic much more tactical. A magical duel is all about preparation, research, and outsmarting your opponent. Forcing yourself through based on enormous mana reserves is possible but wasteful and may leave you powerless to an unexpected trap. I feel like it could make a decent tactics game a la final fantasy tactics and phantom brave. Sitting here after stating that the wheels in my head begin turning the story into a game with incredible speed, but would a novel be a better outlet for the story? The story is about a woman's journey to find the witch who killed her family. She doesn't really have any allies to "join her group" and is pretty much on her own. The gameplay elements that I would implement might make it so that not having other characters to control would be manageable but would it remain interesting through 20 hours of gameplay? Guess I could attempt a few chapters in novel form and also make a gameplay demo. Worst case scenario I could just make both ;)