The last Qualcomm radios were in the 8/8+/X. The X had weaker RF than the 8/8+, although it's hard to say by how much, so I'm not sure if a Qualcomm X would beat an Intel 8/8+ or not. But that's irrelevant now, since you can't buy a X anymore.
Therefore, we're left with the 8/8+. Each is available with Intel or Qualcomm, so the Qualcomm 8 or 8+ would have the best RF performance. The 8+ might have a teeny, tiny edge over the 8 just because it's larger, and has more space for the antennas, and there's less room for human flesh to be in the way, but the difference is negligible.
We'll see soon when tests are done if Intel can overcome 7+ years of inferior performance to Qualcomm in a single year. That seems highly unlikely. However, we really won't know for sure, since there is no Qualcomm version, so we're also looking at the RF design of these new phones, which appears to be rather lousy.
This guy's theory/interpretation of the data is that the Xs Max's design is so bad that even a Qualcomm X20 radio couldn't save it from having lousy reception:
https://www.wiwavelength.com/2018/09/iphone-xs-and-xs-max-mostly-fail-to.html
I'd love to see a direct comparison to the S9+/Note 9, which seems to be the current RF champ.