Is the iPhone's eSim for the home or roaming carrier?

Solution 1:

The eSim can be used both for home and roaming as indicated by Apple's Website:

Here are a few of the many ways you can use Dual SIM:

• Use one number for business and another number for personal calls.
• Add a local data plan when you travel outside of the country or region.
• Have separate voice and data plans.

Solution 2:

The physical and eSIMs both have full functionality in iPhone. You can select whichever you want to use for data, imessage, etc. in Settings.

There are still not many carriers that support eSIM. Going for eSIM as your home SIM makes a lot of sense if you have a carrier that supports it (like T-Mobile) since you will not have to search for a carrier that supports eSIM wherever you travel and want a secondary SIM.

On the other hand, having a physical SIM as your home SIM allows you to buy eSIMs which are sometimes available through the local carriers apps saving you having to buy a physical chip.

Solution 3:

Roaming is a deal between your home carrier and carrier at a country you're visiting. The whole point of roaming is to use your home SIM abroad.

Therefore, to answer your question: both card-SIM and eSIM are for home carriers, not roaming.

If what you want is to avoid roaming and buy a local SIM at the place you're visiting, then the answer is simple. Physical card-SIMs are nearly universal and you can swap them on your own, while not every carrier supports eSIMs and you need carrier assistance to re-sign your phone to a new eSIM. So get an eSIM from your permanent carrier and keep swapping disposable cards.

Solution 4:

There are a lot of countries/carriers where eSIM is not available while every carrier supports regular SIM, so using your T-Mobile line in the eSIM slot makes the most sense.