As one of Qualcomms core businesses they typically excel at modem tech compared to Intel. That doesn't mean Intel is "bad", it just mean they might be "not as good".
Later model Intel modems in the iPhone XS and newer perform very well. Intel closed a lot of the gaps. Keep in mind this is a technological gap not because Qualcomm is innately better (admittedly they are though).
For example 4x4 MIMO is the difference between the two intel equipped iPhones below....
Then it depends on software and modem firmware (you can check that in settings > About).
For example the difference between iOS 11 and iOS 12 (modem firmware) is as big of a difference as Intel vs Qualcomm when the X modem results were relevant as shown....
(keep in mind RSPR is a narrow window here and its bad signal 120-129, except disconnect at 125-129).
The biggest factor is carrier support for a particular person. MIMO and network aggregation are the differences you are experiencing. In my area I might not see any improvements due to network limitations (much like how the 1+ gbit/s cap is NEVER seen due to bandwidth caps and network congestion).
Apple bought Intels modem business to tailor the modem for the device specifically (and likely to acquire Intels patent portfolio). So they might not ever be "the best" they will certainly be the best for iPhones.