Taxi or Uber

While the Uber app will work in Dublin all it does is call a taxi. Uber, as a stand alone alternative to taxis does not exist in Dublin. So you are better off just going to the taxi stand outside the terminal. Unless there is a special event occurring taxis will be plentiful.

Be aware that there is an Airport to Dublin bus that runs that will be cheaper than a taxi. www.aircoach.ie

For 2 or more people with luggage I'd vote for a taxi just for the convenience.
If a solo traveler I'd opt for the bus.