Nb-Iot requires an account with a Telco, plus a simcard for each device.. and you have to be in cellular radio coverage range for your telco.. It's absolutely amazing, but does require that level of commitment to data connectivity.
LoraWAN is much lower barrier to entry, in that any gateway connecting to the right server (see the things network, TTN) will relay your devices data to the right place, and send data back to your device. So you can use someone else's gateway if that exists, or you setup your own gateway...
There's different power consumption and data size and transmit time limitations for both too, but the basic network subscription is the biggest thing to consider first.