SMS or email: when do you choose which?

The two channels do different things. Weighing them against each other on price is the wrong question.

SMS wins on urgency

An SMS is nearly always read, and usually within minutes. That makes it suitable for anything that has to arrive today: an appointment tomorrow, a delivery on its way, an outage, a verification code.

Email wins on content

Anything longer than two sentences, anything that needs images or has to be kept, belongs in an email. An invoice, a newsletter, a manual.

Where it goes wrong

A three-part SMS with a long explanation is expensive and poorly read. An urgent alert by email is only seen the next day. Both mistakes cost money.

The combination

Often the answer is both: the explanation by email, and a short SMS when something genuinely has to happen now. For example an order confirmation by mail and an SMS on the day the parcel is delivered.