Wireless isn’t always as fast, but it’s more convenient. Most wireless iPhone chargers deliver 5W or 7.5W and work through most iPhone cases.
Most standalone charging pads expect you to provide the actual charger brick, and can’t deliver more power than you put into them – so even if an iPhone wireless charging pad can deliver 7.5W, it can’t do that if you’re plugging it into a charger that only gives it 5W.