The mobile app notfications work as long as you have the mobile app installed on all the devices you want notified. My wife and son just do not want "Another dumb app" on their phones, so being able to send texts to them works best for us.
Importantly, I can even send texts to anyone who's mobile number I have. I have some events set up to notify my brother who lives nearby, and all I need to do that was enter his phone number (and get his permission to include him in the notifications). 
I don't use the mobile app at all myself, and send emails and text messages from Hubitat using Sendmail, a community developed email/test messaging driver. You can read more about it here. Free!
