Flank vs hanger steak

Your flank, hanger and skirt are steaks that can not be over cooked . . . . rare to medium rare. Flatiron comes of the clod of the chuck and would be top of list for most flavour, along with the hanger. Skirt is the diaphragm, more coarse, hence used so often in Mexican/SW food, since it is cut into strips or even shredded. So it also depends on the recipe you talk about.

Hanger is not always easy to find because it's a pretty small piece of the carcass compared to flank. Flatiron (or skirt) would be a better substitute. How long to cook depends on how you plan to prepare it and there is no consistant measure of time to pound. Meat is done when it's done. An overnight marinade can help because these are tough cuts, flank being the most expensive. But I always go by internal temperature.

Hanger steak is our most usual cut for a quickly grilled beef dinner. It is absolutely not tough. You many also know it as onglet. If you haven't tried it, do so. You're in for a treat.

No they are completely different cuts of meat. Better to sub skirt for flank almost identical

The most important thing about both cuts of meat is how you cut them, both are tough and must be cut against the grain (which makes them easier to chew because of the way the muscle fibers run). You should not have any trouble with cooking time or texture, they are similar cuts and flank and skirt are often substituted as hanger is not always easy to find.