This comparison has a clean answer and people keep overthinking it. In the US, Canada, the UK and Australia, iMessage and SMS are where customers are. In most of Latin America, India, Southeast Asia, much of Africa and large parts of continental Europe, WhatsApp is the default and a text message reads as strange. Pick by where your customers live, not by feature list.
The structural differences that matter
iMessage (via a provider)
- No template pre-approval — write what you like
- Send first, within consent rules
- SMS fallback reaches everyone
- Priced per line or per message
- US, CA, UK, AU strength
WhatsApp Business API
- Templates pre-approved by Meta
- 24-hour window rules on free-form replies
- No fallback — they have it or they do not
- Priced per conversation
- Dominant across most of the world
The template approval process is the difference people underestimate. On WhatsApp, business-initiated messages must use templates Meta has approved in advance, and changing wording means resubmitting. That is fine for reminders you send a thousand times. It is genuinely awkward for a two-person business that wants to say something specific today.
The 24-hour window
WhatsApp lets you reply freely for 24 hours after a customer messages you. Outside that window you are back to approved templates. This shapes how you run a conversation in a way iMessage does not — and it catches out teams that reply the next morning to a message received at 3pm.
Some providers do both
LoopMessage routes iMessage, SMS, RCS and WhatsApp through one API. If you genuinely serve customers across regions, one integration with per-recipient routing beats maintaining two stacks.
How to decide without guessing
- Pull the country codes from your existing customer phone numbers. That distribution is your answer, and it takes ten minutes.
- If more than roughly a fifth sit outside iMessage-strong markets, look at a multi-channel provider rather than adding a second stack later.
- If you are entirely domestic in the US, UK, Canada or Australia, WhatsApp is a distraction. Build on iMessage with SMS fallback and revisit if you expand.
- If you are primarily serving a diaspora community, ask a few customers rather than assuming from the country code — many use WhatsApp domestically to reach family abroad.
Whichever you choose, the consent and record-keeping obligations follow the recipient's jurisdiction, not the protocol. International rules covers what changes when you cross a border.
Next step
Generate a tagged link for whatever you send next with the UTM builder, see what this looks like in your industry, or compare the services that can send it on the providers page.