I would vote to save the grapevine and let the cherry tree become the scaffolding. This is because I get a lot of questions about diseases on cherry trees, birds eating all the cherries, and problems with insects on cherry trees—but your grape vine seems happy. Encourage the plants that do well in your garden and get rid of the plants that struggle, and you will have a garden full of happy, healthy plants. Keep growing, Marianne Binetti