If you got a A1901 / GSM-only / AT&T / T-Mobile / MQAJ2LL/A iPhone X, it turns out you can still use it to almost full capacity on a Verizon CDMA network.
The first traditional barrier is activating the phone but for the iPhone X, you can activate the phone with just the blank SIM that came with the phone and at least get to a usable phone with WiFi connectivity.
When it comes to using a Verizon SIM, everything’s pretty much plug and play. With carriers around the world deprecating CDMA frequencies, most modern connectivity are based on shared (at least between A1901 and A1865 radios) LTE frequencies. And with a A1901 and a Verizon SIM, you can at least connect to Verizon’s LTE networks.
With Voice Over LTE enabled by default and WiFi calling that you can turn on in the settings, you can even make phone calls and send/receive SMS while connected to LTE/WiFi.
Despite this versatility, given the option, it may still be wiser to get the A1865 model with the superior Qualcomm radio chips and likely better resale value down the road.
The Intel chip iPhone also seems to not support using LTE data during a phone call, reverting to HSPA on GSM networks or no data at all on CDMA networks which could be a hassle if you need to look something up during a conversation and there’s no WiFi.