Blog / Guide

WhatsApp vs SMS: when it's worth using one over the other

Choosing between WhatsApp vs SMS isn't a matter of fashion: they are two channels with different logic, costs and strengths. SMS reaches practically any phone, even without a data connection, while WhatsApp offers a real conversation with images, buttons and real-time replies. In this guide we compare the two channels honestly - open rates, costs, reliability and use cases - to help you decide which to use for each type of message, without slogans.

Open and read rates compared

Both channels have very high open rates compared to email: the vast majority of messages are read within minutes. The real difference lies in the reply. SMS is a mostly one-way channel: the user reads it but rarely replies. WhatsApp, on the other hand, was built for conversation, so the probability that the customer writes back - asking a question, booking, buying - is clearly higher. If your goal is to open a dialogue, WhatsApp starts with an advantage.

Costs: how you really pay

SMS almost always has a per-message cost on a pay-as-you-go basis, which varies depending on the destination country and volume. It's predictable but grows linearly: the more SMS you send, the more you pay. WhatsApp has two tracks with different cost logic.

• Official WhatsApp Meta API: Meta bills conversations according to its own pricing model. SendApp applies no markup on Cloud API messages: you pay Meta directly for the cost of the conversation.
• WhatsApp Web via QR: by connecting your number through a QR code there are no per-message costs to Meta. It's the cheapest route for modest volumes and one-to-one conversations.
• SMS: ideal when you need certainty of delivery even to people who don't have WhatsApp, but with a unit cost that must be calculated campaign by campaign.

Reliability and coverage

Here SMS has a structural advantage: it works on any phone, even the oldest one, and requires neither a data connection nor an installed app. That's why it remains the standard for OTP codes, critical alerts and communications to very broad and heterogeneous audiences. WhatsApp requires the recipient to have the app and a connection, but in Italy penetration is so high that for most B2C audiences this is no longer a real limitation.

When to choose SMS

• Verification codes and OTP: immediate delivery, no dependence on an app.
• Critical alerts and service communications where all that matters is that the message arrives.
• Very broad audiences where you can't be sure everyone uses WhatsApp.
• Purely informational messages that don't require a reply.

When to choose WhatsApp

• Customer support and conversational selling, where the customer needs to be able to reply.
• Messages with images, PDFs, catalogs, buttons and calls to action.
• Cart recovery, follow-up and nurturing where dialogue boosts conversion.
• Appointment reminders that the customer can confirm or cancel in one tap.

Practical rule: use SMS when you just need it 'to arrive', use WhatsApp when you want it 'to get a reply'. Many winning flows combine them: SMS as a safety net when the number doesn't have WhatsApp, WhatsApp as the main channel.

The real advantage: not having to choose

The question WhatsApp or SMS assumes you have to choose one tool for the former and one tool for the latter. That's not the case if you work from a single multichannel platform. SendApp manages WhatsApp (both official API and WhatsApp Web) and SMS from the same address book and the same inbox, so you can decide the channel message by message, or even set SMS as a fallback when WhatsApp isn't available.

How to do it with SendApp

With SendApp Agent you upload contacts once, organize them with tags and create broadcast campaigns using variables like {name}, {phone} and {email}. From there you choose the channel: WhatsApp with approved templates and the green tick through the official API, WhatsApp Web via QR with no per-message costs, or SMS when you need total coverage. All conversations flow into a single multichannel inbox, together with Instagram, Telegram, Messenger, Email, widget and Voice AI. Plans start at 19 euros a month; Cloud API messages remain billed by Meta with no markup from SendApp.