It certainly makes sense for Aer Lingus.
Narrowbodies make sense for a number of routes ex-Dublin and would be of huge advantage to Shannon services or if they were ever to launch trnsatlantic from Cork. It makes particular sense in the last case as they can still keep a uniform fleet in Cork.
A cynic might suggest that Aer Lingus already know the answer to the question, that one works and one doesn't and that they will use this to drive down the cost of the one that doesn't.