This kind of comes down to preference, or what you have available, but generally you're going to want a variety of apple that will hold its shape after baking and not turn to total mush. We had a huge bag of Honeycrisp apples (my personal favorite) to use up, so that's what I used. Granny Smith are usually considered the best apples for apple pie, but Golden Delicious, Braeburn, and Pink Lady apples would all work well for this apple crisp recipe, or for a pie.