I have nothing to compare to but I can't imagine there is a noticeable difference in signal quality between the two in this day an age.  That doesn't mean that certain carriers are not doing some sort of quality of service management on the back end to give certain users priority but in terms of signal strength they all have comparable radios.

There was a thread on here recently about turning off 5g on a phone.  Every evolution of network speed upgrades so far has caused a decrease in signal strength/quality in fringe areas until the network is built out enough to handle the new frequencies.  Faster frequencies tend to have less ability to penetrate materials and their wavelength doesn't travel as far.