I would love to say the bigger the better, and Technically the answer is yes but in practice there are just too many variable's on on 4G/5G Mobile Networks and Mobile Devices, Coverage, Signal Quality of the Cell Mast, Signal Strength to the Device, Type of Data Connection, Router Positioning, Network Congestion, Time of Day, etc, the list goes on and on, so there is never going to be any guarantees.
What I will say is that a 4/5G Home Router over its smaller MiFi Device is going to have a better opportunity to deal with the Mobile Data Signals Trickery, its probably going to be higher specked to start with, the internal Antennas will be bigger and a better design over its smaller counterpart, its CPU Processer will run cooler and it will probably provide a better Indoor WiFi Coverage and have better Ethernet Cable options, so it does really start to tick all the right boxes.
One thing to consider between to two would be overall consistency and stability and the Home Router should provide this over a smaller Battery Device.
