Our best practice advice is to create with the alert action the 'Log to Orion Event Manager' action. The reason for this is that the event message can be viewed for longer than the Alert history information and that the content of this can be written out in a more usable and easily readable manner. Just think of events in this context as being a method to record textual content in a more controlled manner than the alert content. However, since SolarWinds added the Alert description field which can take this, the use of events as an output action has lessened. The choice is yours on which to use.
Events could also be used as a filter within other alerts, so I have done this before when the creation of event messages can trigger new alerts.