You don't need an iPhone 6
But you should get one. Sure, it's better for reading, for photography and for staying connected but most of all, you're probably already paying for it. If you're locked in to one of the big providers, they've been subsiding your current phone, which is probably slow to respond but quick to drain its battery each day. You've paid off that subsidy months ago yet your bill hasn't dropped. Go trade in your current phone and get a 6 or 6+.