Is it more economical to get a network railcard or under 25 railcard?

I want to get a railcard, but I am unsure whether to get a network railcard (which covers the South East England and London regions) or to get a 16-25 railcard. My confusion stems from the fact that they are both the same price and cover the same area, but I struggle to see the difference between the two cards, unless I've missed something. Please can someone clarify if it would be better to get a 16-25 railcard or a network railcard for someone under 25?