Distinguish the technology
A cellular router depends on mobile signal; a fixed service relies on address-based infrastructure. Use the correct availability check. A phone test outdoors does not establish performance for either service indoors.
Consider the household
Video calls, uploads, gaming and simultaneous users have different requirements. Router placement and internal Wi-Fi can also affect experience. Read equipment return, commitment and usage conditions.
Consider other equipment
Home voice, alarms and telecare may depend on the connection. Ask the equipment supplier about compatibility and power cuts before changing service. A common brand does not mean one cancellation process covers every product.