A property manager in Houston has two tenants with leaky faucets. One texts the office number. The other sends a WhatsApp message with a short video of the drip. Both expect a reply today, and both are perfectly reasonable ways to reach a business.
For US businesses, the question usually isn’t “SMS or WhatsApp?” It’s “which channel fits which customer and which kind of conversation, and what does each one require to run properly?” The two channels differ in reach, media, setup, rules for business-initiated messages and how costs work.
This article compares them on the dimensions that matter for a small team, then gives you a decision table you can apply to your own conversations. It’s general information, not legal advice. Messaging rules change, so check the details with your provider and, for compliance questions, your counsel.
The short version
- SMS works on virtually every mobile phone in the US without the customer installing anything. It’s the default for many US customers, and it’s well suited to reminders, quick confirmations and first contact.
- WhatsApp requires the customer to have the app, but offers richer media, read receipts and a better experience for longer, detailed conversations. Many customers with international ties already use it daily.
- Many businesses end up using both, and the real challenge becomes keeping one history per customer across channels.
Reach: who can you message?
SMS reaches any mobile number capable of receiving texts. The customer doesn’t need an app or an account. That makes it the safest default when you don’t know a customer’s preferences.
WhatsApp reaches customers who have installed WhatsApp and registered their number. In the US, usage is uneven: some customers use it constantly, others never have. Customers who travel, have family abroad or come from countries where WhatsApp is the main way to message often prefer it.
The practical takeaway: don’t assume. Ask, or watch which channel customers choose when they contact you first. If a customer reaches out on WhatsApp, reply there.
Rich media and conversation experience
SMS is text-only. Standard SMS messages are split into segments: up to 160 characters per segment with the basic character set, and fewer (70) when the message contains characters like emoji or many accented letters. Long messages are sent as multiple segments, and each segment may be billed. Photos and videos require MMS, which has its own size limits and costs, and quality can be reduced in transit. Our SMS segment calculator shows how a given message will be split.
WhatsApp supports photos, videos, documents, voice notes and location sharing, generally with better quality than MMS. It also shows delivery and read indicators (when the customer hasn’t turned them off). For conversations that involve photos of a problem, documents like quotes or a long back-and-forth, WhatsApp often feels more natural.
Registration and approval
Both channels require setup before a business can message at any real volume, and the processes are very different.
SMS: 10DLC registration
Businesses sending application-to-person (A2P) texts from standard 10-digit US phone numbers generally need 10DLC registration. In broad terms, your messaging provider helps you register your brand (your business identity) and one or more campaigns (what you’ll use texting for, such as customer care or appointment reminders), along with sample messages and a description of how customers opt in.
Things to know:
- Registration is usually done through your messaging provider, and review can take time.
- Unregistered or poorly described traffic may be filtered or blocked by carriers.
- Your campaign description should match what you actually send.
- Consent matters. You’ll be asked how customers opt in to texts.
Our guide to US business texting compliance covers the concepts in more detail.
WhatsApp: the WhatsApp Business Platform
To message customers from a business system (rather than the free WhatsApp Business app on a single phone), businesses use the WhatsApp Business Platform, typically through a provider. Setup involves a Meta business account, a phone number dedicated to the platform, a display name that goes through review and, in many cases, business verification.
Things to know:
- A number registered on the platform generally can’t be used at the same time in the regular WhatsApp or WhatsApp Business app.
- Meta’s commerce and business messaging policies apply, including restrictions on certain types of businesses and products.
- Customers need to have opted in to receive messages you initiate.
Templates and the 24-hour window
This is the biggest operational difference.
On WhatsApp, when a customer messages you, a customer service window opens for 24 hours from their latest message. Within that window, you can reply freely. Outside it, you can only start a conversation with a pre-approved message template. Templates are submitted for review and categorized (for example as marketing, utility or authentication). That means appointment reminders, follow-ups after a week of silence and post-sale check-ins all need approved templates ready to go.
Example utility template: Hi {{1}}, this is a reminder of your appointment with Ridgeway Plumbing on {{2}} at {{3}}. Reply here if you need to reschedule.
On SMS, there’s no equivalent template approval step for individual messages. Your messages still need to match your registered campaign, respect consent and opt-out requests (like STOP) and follow carrier rules, but you can write each message freely.
In practice: WhatsApp rewards planning. Draft your common outbound messages as templates early, because you can’t improvise a first message to a customer whose window has closed.
Cost structure in general terms
We won’t quote numbers, because prices change and vary by provider. But the structure is worth understanding:
SMS costs typically include:
- Your provider’s per-message (or per-segment) charges, with MMS priced differently
- Carrier fees that are passed through on business messages
- 10DLC brand and campaign registration fees
- Phone number rental
WhatsApp costs typically include:
- Charges set by Meta for certain messages, which depend on factors like the message category and the customer’s country. Meta has changed its pricing model over time, so check the current version.
- Your provider’s fees on top, if any
- Replies within the customer service window are generally treated differently from business-initiated template messages
Long messages cost more on SMS (more segments). Marketing templates often cost more on WhatsApp than utility messages. Ask your provider for a clear breakdown based on your expected mix.
Customer preference and consent
Whatever the channel, the customer’s preference should win. A few practical habits:
- Mirror the channel. If a customer starts on WhatsApp, continue there.
- Ask once, record it. “Is text or WhatsApp better for updates?” Then store the answer on the contact.
- Respect opt-outs on every channel. An opt-out on one channel is a strong signal about the relationship overall.
- Don’t duplicate. Sending the same reminder on both channels annoys people.
Decision table: which channel for which conversation
| Conversation | SMS | Notes | |
|---|---|---|---|
| First reply to a new lead | Good | Good | Use whichever channel the lead used |
| Outreach to a lead who hasn’t messaged you yet | Possible with consent | Requires opt-in and approved template | Check consent rules with your provider/counsel |
| Appointment reminders | Good | Good, with a utility template | SMS is the safe default if you don’t know the customer’s preference |
| Quotes, documents and photos | Limited (MMS) | Strong | WhatsApp handles files and images better |
| Long, detailed back-and-forth | Workable | Strong | SMS segments add up on long messages |
| Quick confirmations (“On my way”) | Strong | Good inside the 24-hour window | |
| Follow-up after a week of silence | Good | Requires an approved template | Plan WhatsApp templates in advance |
| Customers with international ties | Workable | Often preferred | Ask; don’t assume |
| Promotional messages | Requires consent and a matching campaign | Marketing template; requires opt-in | Rules and costs differ; check with your provider |
Use this as a starting point, then adjust based on what your customers actually do. Our article on communicating with customers after the sale covers reminders and updates in more depth.
The real challenge: one history across both
Most small teams that support both channels run into the same problem: the conversation splits. A customer texts on Monday, sends photos on WhatsApp on Wednesday and calls on Friday asking “did you get my pictures?” If texts and WhatsApp messages live in different apps, or on different people’s phones, nobody has the full picture.
Whatever tools you choose, aim for one place where every message from a customer lands, regardless of channel, with one owner and one history.
Where inChat fits
inChat is a conversation-first CRM for small US teams, and it’s in development with WhatsApp and SMS as its launch channels, both in one team inbox with one history per customer. It’s designed so you can reply on whichever channel the customer chose, with a shared business number that stays with the company. If you’re working out how to run a shared business number across channels, you can request early access to follow along.