Compatibility is the first filter
Confirm that the phone supports eSIM and is carrier-unlocked before looking at price. Apple directs travellers to check for ‘No SIM Restrictions’; an incompatible or locked phone cannot be rescued by a cheaper plan. Keep the activation QR code private.
Compare the product, not the headline
Record trip length, included high-speed data, any speed reduction, hotspot permission, activation point and top-up method. ‘Unlimited’ can still have speed or fair-use conditions, while a fixed allowance can be better for a light user. Read the live terms before purchase.
A Korean number is a separate requirement
eSIM describes installation technology, not whether the plan includes voice, SMS or a local number. Many travel eSIMs are data-only. Buy a number-enabled plan only when a named reservation, verification or calling task genuinely requires it.