Airport

Why don't you fly open jaw into one and out of the other? With one of the national car rental companies, you could return the car at the other end.
We were there last year, and drove from Dublin about 225 miles to the southwest corner of the country. Driving in a foreign land is tough if you're not familiar with driving on the left side of the road. But the roads are narrow and rough. Get off on the backroads, and there are ditches, walls and scrub brush right up to the pavement. It takes a better than average driver to navigate the roads of Ireland.

We flew into Shannon, rented a vehicle there, and returned it in Dublin. I am glad we planned the trip that way. There is much less traffic near the Shannon airport than near Dublin. It was nice to get used to driving in the place where there was less traffic. The Shannon airport was also less busy. We were the only people in the car rental line and it took less than 5 minutes until the keys were in our hands (we did pre-book online). There was also an automatic available for us at Shannon as we had booked. I have heard from others who booked an automatic, but when they went to pick up the vehicle, only manuals were available. (Yes, this could happen at any rental location.)

Agree with the open jaw, but if for some reason you need/want to fly into and out of the same airport, choose Dublin. This is assuming you want to spend time in Dublin. If you rent and return a car to Shannon you will have it when you visit Dublin. A car in Dublin will be completely useless and in addition you will have to pay the daily car rental cost and the cost of parking for those days (expensive). If you fly into and out of Dublin, you can tour Dublin first and then rent the car and just turn it in at the Dublin airport when you are done touring Ireland.

Many years ago on our first trip to Europe we made the mistake of flying into and out of Shannon. The above is what we learned on that trip and have applied the same principle to all trips since then, that is fly into a major city and tour it before picking up your car. Also if our return flight is from a different city, we turn the car in when we arrive in that city, then tour the city for however long we want to and then take public transportation to the airport. Saves a lot of hassle, car rental fees and parking fees.

If you plan on going to the west coast, then fly into Shannon and out of Dublin. Or Vice Versa. No reason to spend your time driving to where you want to go if you can just fly there to begin with.

Shannon is a much more user-friendly airport, and that extends to the car rental as well. And navigating out of it is so much easier than Dublin's. Also agree with Bob's point that if you're spending time in Dublin, do it at the start or end of your trip when you've either not picked up your car yet, or have already turned it in..

I paid around $70 as a drop fee on a one way rental car but otherwise you should consider open jaw. If you are going to include Galway landing at Shannon and taking the bus can save you days in your rental. Also saves you from having to drive right off the plane. Then take the bus back to pick up the car. Also, get the super CDW, my experience suggests that charging “whatever we want” as they put it for a bumper scratch that may or may not have happened on my watch was part of the monetization plan. We’re talking here about the underside of the bumper and nothing near bad enough they would actually take the step of fixing. I have the zero deductible so it did not matter.