My wife and I and another couple are considering renting a cottage for a week in one part of Ireland and then for another week in a different area of Ireland. We would like to know whether we could take a bus to villages and sites of interest rather than rent a car or is a train better?
My experience is that renting a car is better than their bus service, especially if you are traveling to small villages and out of the way sites. With two couples sharing the cost, it will probably not be much more expensive either.
I have always rented a car in Ireland and found it to be the best for me.
I traveled around by bus for a summer a never had a problem getting to my destinations. Bus Eirann has detailed schedules. You might have to change buses in a town or two, but if you're out to save money as I was, it is definitely possible. And you get to stop in towns on your way to have lunch or walk around and check it out.
I've travelled both with and without a car in Ireland. I never had a problem with any of the larger coach buses (Bus Eirann) that cover both large cities and smaller towns.
Will say that if you are based in a smaller village, you may find the local bus service is not as frequent as you want it to be and sometimes cannot be relied upon. As an example, I hopped on a local bus running between Kinvara and Galway in Western Ireland and the bus got full. The driver would not accept any more passengers and refused to let 5 people board because he couldn't have anyone standing in the aisle. There are only a few buses each day that drive this route, so those left behind had a very long wait until the next bus.
Also, bus service can be more frequent in the summer months and cover more sites of interest. If you are travelling outside of the summer, you might rethink the car rental.
Train service is fairly limited except between large cities.