Not an open-rate argument - the two channels have genuinely different mechanics. One requires no permission and cannot be replied to; the other requires templates and gives you a conversation. Which each is actually for.
Key takeaways
- SMS has no permission gate and no template approval. That makes it the reliable fallback and the right channel for anything that must go out now, like a one-time code.
- WhatsApp gives you a conversation. That is its real advantage - a customer can reply, and the exchange becomes a record - and it is exactly what SMS with an alphanumeric sender cannot do.
- WhatsApp costs a setup, not just a per-message fee. Business verification, webhooks, number registration and template approval all take time before the first message goes out.
- The right answer for most businesses is both, with a documented fallback rule - and the fallback direction is almost always WhatsApp first, SMS when it fails.
This debate usually runs on open rates, and I am not going to quote figures I have not verified. The difference between the channels is not statistical - it is structural, and their differing mechanics are what determine which suits which scenario. That is what can be said with confidence.
The differences that decide
| SMS | WhatsApp Cloud API | |
|---|---|---|
| Permission before sending | None - any valid number | A 24-hour window and approved templates |
| Initiating contact | Free text, always | Approved template only |
| Customer can reply | No, with an alphanumeric sender | Yes - and that is the point |
| Length | 70 characters per segment in Hebrew | No practical limit |
| Media | No | Images, PDFs, location |
| Setup time | Hours | Days to weeks |
| Cost model | Per segment | Per conversation, not per message |
Why SMS is still needed
It is easy to dismiss as dated. That is a mistake, for two structural reasons:
There is no gate
You can send an SMS to any valid number, immediately, with no prior permission and no template anyone has to approve. That makes it the one channel that is always available.
Which is why it is the right choice for a one-time code: it must arrive now, it needs no conversation, and it cannot wait for template approval. Even a customer without WhatsApp receives it.
It is the fallback
And hence the important part: when WhatsApp fails - error 131026, the recipient has no WhatsApp, or they blocked you - SMS is what remains. A system with only one channel has no fallback.
The cost: Hebrew
A Hebrew SMS holds 70 characters per segment instead of 160, because Hebrew forces the wider encoding. The budget implication is detailed in the SMS guide, and it is worth knowing before planning a campaign.
Why WhatsApp - and it is not what most people say
The argument usually heard is "people read it". The structural argument is stronger:
The customer can reply
That is the real difference. With SMS using an alphanumeric sender - what most businesses use - the recipient simply cannot answer. The message is a one-way street.
On WhatsApp they can. And a customer's reply is a lead: someone who expressed interest, in a channel where the conversation can continue, while they are there.
And the moment they reply, a 24-hour window opens in which free-form text can be sent. The channel turns from a broadcast into a conversation - which is what SMS does not do.
The exchange becomes a record
With the Cloud API the conversation is stored, can be assigned to a rep, and is documented. That is the gap most Israeli businesses live with - sales conversations running in a channel with no follow-up.
The cost: it is not immediate
Before the first message: business verification, webhook configuration, number registration and template approval. The setup is not trivial, and it is measured in days to weeks rather than hours.
What that means practically: if something must go out this week, WhatsApp is not the answer for this week. Start the setup in parallel with development rather than after it.
What people get wrong in planning
Two recurring false assumptions:
1. "We'll send whatever is in the notes field over WhatsApp." No. An initiated message must be an approved template with positional variables. You cannot compose dynamic text. Anyone planning without knowing this discovers it in testing and redesigns.
2. "We'll move all SMS to WhatsApp and save money." The cost model differs - WhatsApp is priced per conversation rather than per message - so the comparison depends on your usage pattern, not on a per-message rate. A business sending one message per customer behaves differently from one running an exchange. Calculate against real volume before promising a saving.
The recommendation: both, with a fallback rule
For most businesses the answer is not to choose. It is to design both channels with a documented rule:
| Scenario | Channel |
|---|---|
| One-time code | SMS - must arrive now, needs no conversation |
| Order confirmation, reminder | WhatsApp, falling back to SMS on failure |
| Sales or service conversation | WhatsApp - because the customer needs to reply |
| Critical alert | Both. The cost is negligible against the failure |
What makes this a system rather than two scripts
- Record on the customer what works. A number that returned 131026 is not worth retrying on WhatsApp - flag it and go to SMS next time.
- One E.164 normalisation serving both channels.
- Customer preference, where expressed. Someone who asked to stop receiving on one channel should not receive the same content on the other - that reads as circumvention, because it is.
- Cross-channel idempotency. One reminder, not one per channel.
How to decide
- Does the customer need to reply? WhatsApp. That decides it alone.
- Must it arrive now? SMS - no gate and no template approval.
- Is there time for setup? If not, start on SMS and stand up WhatsApp in parallel.
- Calculate cost against real volume, not a per-message rate.
- Either way: design a fallback. A single channel is a single point of failure.
Frequently asked questions
Should a business use SMS or WhatsApp in Israel?
Usually both, with a documented fallback rule. SMS suits anything that must arrive immediately and needs no reply - a one-time code above all - because it has no permission gate and no template approval. WhatsApp suits anything where the customer should be able to answer, because a reply is a lead and it opens a 24-hour window for free-form conversation.
Can customers reply to an SMS from a business?
Not when it is sent from an alphanumeric sender name, which is what most businesses use - the message is one-way. That is the structural difference from WhatsApp, where a reply is possible and turns the message into a conversation. If your flow expects an answer, an alphanumeric SMS sender will silently break it.
Is moving from SMS to WhatsApp cheaper?
It depends on your usage pattern, not on a headline rate. WhatsApp is priced per conversation rather than per message, so a business sending one isolated message per customer behaves very differently from one running an exchange. Calculate against your real volume and message pattern before promising a saving, and remember WhatsApp also costs a setup measured in days to weeks.
Why is SMS still the right channel for one-time codes?
Because it has no permission gate and no template approval, so it can go to any valid number immediately, including customers who do not use WhatsApp. A one-time code must arrive now and needs no conversation, which is exactly SMS's shape. It is also the fallback when WhatsApp returns an undeliverable error.
What makes a two-channel setup a system rather than two scripts?
Recording on the customer record which channel works, so a number that returned an undeliverable error is not retried on WhatsApp; one E.164 normalisation serving both; honouring a customer's opt-out across channels rather than using the other one as a workaround; and cross-channel idempotency so a reminder goes out once rather than once per channel.
Keep reading
Related service
WhatsApp Cloud API
Templates, a two-way inbox and reminders on the official Meta API.
About the author
Yehonatan Saadia
Freelance automation, web & MVP engineer
I'm Yehonatan Saadia, a senior engineer who builds business automation, custom websites, and MVPs for small and mid-sized companies across the US, Europe, and Israel. These guides come from real client work, not theory.
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