Aren't efficient DC-DC converters just switching power supplies? Are they inherently more efficient or long lived than a 120VAC-DC switching power supply? I'm

Aren't efficient DC-DC converters just switching power supplies? Are they inherently more efficient or long lived than a 120VAC-DC switching power supply? I'm using my ipad while plugged into a 120V USB charger, and the charger isn't even warm.