The Swedish Firesteel is a very useful device. I’ve had one for years and suggest you do as well if you have any interest in wilderness survival, camping, or backpacking. Compared to a magnesium bar, the firesteel is a more durable tool simply because it is a much larger piece of flint. The only drawback I’ve found is the rather large finger hold, which makes it very difficult to conceal (such as on a necklace under your shirt) but certainly makes it easier to hold when you really need to.
If you’ll read my review of the magnesium flint you’ll see why I recommend a a good quality firesteel over the magnesium bar. If money is a major concern then just get a $5 magnesium bar from Walmart and call it a day. Of course, this Scout model of firesteel only costs a bit more than a magnesium bar.