In the US, while many I know use iMessage or Android send via SMS/RCS, most all my friends and family also have Facebook Messenger and most all seem to end up sending there since one doesn't have to worry about if Apple/Android, or which features are supported etc. The only big downside is Facebook Messenger strips all meta data, so unlike say Apple Messages, not good for sending photos to friends family since won't have the correct date, location, etc (which you can turn on/off on Apple Messages), and with messages can send as large or as many as I want in one message so they can easily add to their Photo library with a click. With Facebook Messenger, even with the new HD feature (you annoying have to click each time), you still have limitations on how many and size you can send. Hoping Messenger or or WhatsApp eventually seamlessly support that. Some apps say they do but you have to add photo as a "file" which ends up with lots of down sides from a user experience. Also if WhatsApp is so popular hopefully eventually they let you merge your Messenger data into What's App since can't imagine starting in a new app and losing a lifetime of messages history. Was excited for RCS, but so far, has been problematic where sometimes RCS is enabled for a contact other times for same contact its not. Or slow to send, though is preserving meta data it seem now. But no support for replies, which is a deal breaker and of course not encrypted at all.