Choosing the correct LTE modem is simple when you understand the basic principles.
Let’s keep things simple and call the LTE modem the heartbeat of your IoT hardware. The modem will be a major driver of speed and performance. The higher the modem category the faster and higher performance you get and as general rule, the higher the modem category the higher the cost. So it is just a case of getting what you pay for.
That said, there are some IoT applications which will not need a high specification modem so there is no benefit whatsoever to incurring extra cost on the higher specification models. For example if your solution was transmitting small data packets from areas of good mobile coverage there would be little benefit is using a modem with the performance of a rocket launcher.
On the other hand if your application was transmitting large amounts of data in short bursts you would want the absolute best speeds possible and in this instance probably opt for a higher category modem capable of transmitting the data in a reliable and timely manner.
Here is a brief description of some of the LTE modem categories you will notice form part of your
hardware specification and broad examples of the kind of applications that might use them.