My wife and I are going through the same process. Consumer Reports has a good report on which low cost providers use what services (e.g.: Verizon towers) so if you have good Verizon service in your area, you might look into one of the low cost services aligned with them.
Its nearly impossible to do a “side by side” comparison and Consumer Reports acknowledges that as well.
We have lousy Verizon service (signal strength) in our area. And it’s the best available at our location, partially due to some grain silos that went up and block the nearest tower.
Last fall I did some investigating of setups where one basically gets a hotspot that works back through our (fiber optic) internet service, but, the equipment was pretty pricey.
:-(