>>janand+(OP)
The problem I have seen is when I need it most, due to a rare fiber internet outage, so does everyone else nearby and cellular data becomes saturated and unusable.
>>dismal+4D
You may or may not be aware, but all plans rack and stack somewhere in a priority list called QCI (Quality of Service Class Identifier). AT&T, for example will put at QCI 7-9 depending on your plan.