LTE-M is a good decision for multiple reasons:
- It supports HTTP(S) so I can directly reach my cloud endpoint without the need to build new CoAP/UDP proxies.
- Roaming. Virtual MNO’s like ibasis offer great coverage for LTE-M in many countries with a single SIM. This saves a lot of headache for global products. I have yet to see a similar offer for NB-IoT.
- Larger data bundles. Generally LTE-M data is cheaper and can be bought in larger quantities. This means I can ocasionally roll out an update without blowing up my data bundle.
- It supports most low power features (except RAI) and increased coverage benefits.
The biggest advantage I see today for NB-IoT is ability to use release assist (RAI). RAI has proven to be the biggest energy saver for simple TX only sensors and the fact none of the LTE-M networks or modules supports it is a major drawback for LTE-M. I understand this will be adressed in coming 3GPP releases but those are months if not years away. The fact that RAI is available today for NB-IoT means it will always beat LTE-M in energy consumption.