I found the reader was easier to pick up the NFC than my iphone (which needed much more precision to find the antenna for a scan). The reader just needed waving vaguely in the direction of my arm!
The phone was convenient, had better data display, and meant carrying a bit less kit, bit I found the glitchiness of getting the NFC to find the sensor was too annoying, so tended to use the reader. You can use both phone and reader at the same time, but the alarms only sound on the device that activated the sensor first. 🙄