From what I have seen the Intel and Qualcomm modems (I believe ATT and T-Mobile have Intel) are fairly comparable, as Apple supposedly limited the Qualcomm chip so it was on par with the Intel, and that the gimped Qualcomm chip is comparable to that in the iPhone 6s (hat is the generation where T-Mobile iPhones start being able to access the lower frequencies and hence better building penetration. Apple is using both suppliers this generation so that Qualcomm has to compete. I also believe Galaxy phones in general get better reception this generation.
Look through Reddit for a lot of analysis on this. One example:
https://www.reddit.com/r/tmobile/com...ok_at_the_new/