The one-sentence answer
For most travelers: eSIM is cheaper than roaming and more convenient than a local SIM. The exceptions are short trips where roaming is included in your plan, or long stays in a single country where a local SIM is cheapest per GB.
Side-by-side comparison
| Factor | eSIM | International Roaming | Local SIM |
|---|---|---|---|
| Cost (2-week Japan trip) | $6.75 for 5 GB | $10–$15 per day ($140–$210) | $5–$20 at convenience store |
| Setup | Buy online, scan QR code at home | Zero — already active | Buy in-country, show passport |
| Keeps home number | Yes (dual SIM) | Yes | No — new number |
| Multiple countries | Buy per-country or regional plan | Usually works everywhere (at high cost) | New SIM each country |
| Phone lock required? | Must be unlocked | Works on any carrier phone | Must be unlocked |
| Risk of bill shock | None (fixed price) | High — per-MB overage possible | None (prepaid) |
Real cost examples
Two weeks in Japan, typical tourist usage (navigation, social media, messaging, occasional photos):
- International roaming (AT&T International Day Pass): $10/day × 14 days = $140.
- International roaming (T-Mobile Magenta plan): $5/day or included — best roaming value if you have this plan.
- eSIM from Flysimio (5 GB / 30 days): $6.75 total.
- Local SIM from 7-Eleven at Narita Airport (IIJ 10 GB): approximately $20 — comparable to eSIM but requires an in-store visit and passport.
When international roaming is the right choice
- Your plan already includes free international roaming: T-Mobile Magenta, Google Fi, and some Verizon plans include roaming. Free beats cheap.
- Very short trip (1–2 days): the setup time for an eSIM may not be worth it for a 48-hour layover. A daily roaming add-on ($10–$15) is simpler.
- Your phone is carrier-locked: if you cannot unlock your phone, roaming is your only option.
- You receive frequent verification SMS: bank OTPs, work 2FA — roaming keeps your home number fully active for SMS.
When a local SIM beats an eSIM
- Long stays (1–3 months) in a single country: local carriers offer month-to-month prepaid plans that are cheaper per GB than any eSIM for extended stays.
- Your phone does not support eSIM: older phones (iPhone X and earlier, many Android phones from 2019 and before) need a physical SIM.
- You need a local phone number: for job applications, banking, or extended rental agreements in your destination country.
The dual SIM trick: use both
Most modern smartphones support dual SIM — one physical SIM plus one eSIM (or two eSIMs on newer iPhone models). This means you can keep your home SIM active for calls and SMS — so banks can still reach you, incoming calls still land — while the travel eSIM handles all data at local prices. You get the best of both options.
Frequently asked questions
Should I get eSIM or use roaming?
eSIM is almost always cheaper. International roaming from US carriers typically costs $10–$15 per day. A Japan eSIM from Flysimio costs $6.75 for 30 days. The only time roaming wins is if it is already included in your plan (T-Mobile Magenta, Google Fi) or your trip is under 48 hours.
Should I turn off roaming if I have an eSIM?
Turn off Data Roaming on your home SIM and enable it on your travel eSIM. This prevents your home carrier from billing you while letting the eSIM connect to local networks. On iPhone: Settings → Cellular → tap each SIM line individually to set roaming per line.
What are the disadvantages of eSIM?
Three real disadvantages: (1) your phone must be unlocked and eSIM-compatible; (2) setup requires a QR code scan before departure; (3) you cannot physically swap to another device in an emergency. For most travelers these are minor trade-offs against the cost savings.
Is eSIM cheaper than roaming?
In almost every case, yes. A 30-day Japan eSIM from Flysimio is $6.75. AT&T International Day Pass in Japan is $10/day — that is $140 for the same two-week trip. The exception is plans with free international roaming already included.