We fly into Dublin on the 14th of May, and out of Heathrow on the 30th. Our last trip to England we rented a car for two weeks, drove all over, and returned the car to the same rental location before departing. This time we are dealing with a different location for arrival and departure and we have yet to make an itinerary. We are looking for some input on transportation. Our time in England will be short as we have spent quite a bit of time there in the past so most of the time will be in Ireland and Scotland. We are comfortable driving but expect to do a mix of car, train, maybe ferry, and/or "hopper" flights between cities if necessary.
I can't speak for Ireland but in Scotland it will really depend on where you want to go. I have done whole 2 week trips on just trains and buses, but for more remote places a car would be convenient.
I would rent a car in Ireland and use public transportation in Scotland and England because you really need it it Ireland but you don't in Scotland/England unless your going to a very remote place.
In Ireland public transportation may be adequate. I haven't been there recently, but traveled by train and bus (coach) in 1999) across the island and around the edges to Belfast, then Dublin. If you are comfortable with the car option, it would probably be more satisfying to drive yourself. What I like about public transportation in Europe, especially in England and Ireland, is that's where I meet and talk to people. I've had numerous interesting conversations on trains.
Thank you for all of the input. We do enjoy driving and stopping in small towns so likely will want to rent in Ireland for sure. We will definitely consider the public transportation in Scotland. Most of our time will be divided between Ireland and the Edinburg area in Scotland as we only have 16 days.