I think it comes down to two things: how you want to use the tortillas and which you prefer.
Flour tortillas are very soft and pliable with a neutral sweetish flavor. They are almost always used just as they are out of the bag for things like burritos, soft tacos, and enchiladas. Once they go stale, you can use them for quesadillas or migas, but they're not that great fried or made into chips. Try using them when you want a very soft texture or when you want the flavors in the filling to really shine.
Corn tortillas are also quite pliable, but with a more firm and chewy texture. They have a robust flavor of toasted corn, something to take into consideration when using them in a recipe. Corn tortillas are also more versatile. They can be used for soft tacos when they're fresh, but are also fantastic fried to a crisp and used for hardshell tacos, taquitos, or corn chips.
A recipe won't be ruined if you come home with the wrong kind of tortilla in your bag. In fact, you might even want to switch up a recipe you've made several times by trying the other kind of tortilla!
Do you have a preference for one kind of tortilla or the other?
(Image: Emma Christensen)