On Wednesday, August 28, 2019 at 12:45:13 PM UTC-4, wrote:

The text messages should be plain SMS without attachments, and only have links to the "media", which should be stored on the event's web page. And contestants should be able to choose email rather than SMS (still only links). And hopefully be able to get within range of WiFi before downloading anything large - at the time/location and using the tools of their choice. "Don't call us, we'll call you."

If WiFi is not available then WhatsApp would also be expensive or unavailable to some, no? Conversely, some places (including both of the airports where I fly, in the USA) don't have cellphone coverage, at least for some (major) service providers.

SMS is by design an unreliable system for sending token messages for password resets. Something like 5 percent of messages are never delivered and a larger fraction are delayed. I'd find it completely incredible that someone would advocate the use of this for group messaging in 2019 but here we are having a discussion via another obsolete curiosity that predates the Web.

WhatsApp works seamlessly across many types of devices, delivers messages reliably, works with any source of connectivity, is widely installed, can deliver a message over 160 characters in length without jumbling it, and can even transmit a photo. Bruce makes a strong case for Telegram. Either way these apps are faster and more reliable than email or SMS.

Unlike many email clients WhatsApp will automatically resize media to ensure quick and affordable transmission. That is one reason it became popular worldwide. Unlike email your messages will not be bounced back for arbitrary reasons at the destination.