I guess both. On mine, the cigar lighter and accessory plug are on the same circuit.
The reason I ask is that I found an integrated digital volt meter/USB panel that I would like to power from that circuit, but I was wondering if the display being constantly on would eventually drain the battery.
It probably won't cause any issues as it's just milliamps, but I'd rather have it come on and go off with the ignition. I don't really want to run more wires for just a voltage monitor circuit. I guess I could just not hook up the volt meter too.