It isn't just the network but also a MVNO's data prioritization on that network https://www.reddit.com/r/NoContract/..._carriers_and/ I went from Verizon Prepaid with QCI9 to US Mobile Warp with QCI8 (higher priority on congested networks) on a recent model iPhone. I'm able to get data signal with USM Warp in a few places where Verizon Prepaid was severely throttled to the point it didn't seem like it worked. It also gave me 5G UWB in a couple places. Verizon Prepaid didn't support UWB on my plan at the time.

If your frequent routine places are fairly set like mine are, I'd advise subscribing for a bit and checking your coverage before you port. It does mean paying for an extra phone plan if they don't have a free trial program but can save some headaches. One of the places I go has decent signal with T-Mobile but very little with Verizon and AT&T.