My preference is to have multiple points of contact. Email+phone and the alert is sent simultaneously both ways. This happened recently when a purchase I made was flagged. I got a text asking to approve the charge. Not trusting SMS I checked my email and saw the same message as the text and a link to take further action.

I was disappointed that no alert was sent through the banking app. That would be the most secure option but is explicitly disallowed in the notification settings.