Dublin Pass

The answer for any pass of this sort depends. You have to figure out an itinerary based on interests, time and transport. Add up the costs of each stop and see which is cheaper. As to details, the company website https://www.dublinpass.com lists all the sights included and additional details under the "Learn More" button. Trip advisor has about 300 reviews on this so you might want to read thru them.

The Hop on Hop Off tour bus is only good for one day. I don't think that you can get your moneys worth on a 1 day pass but a 2 or 3 day pass will probably save you money. Make sure you do all of the things that cost the most money. If you want to do the Guinness tour you skip the line and don't have to make a reservation for a certain time that will save you time because you don't have to stop what you are doing and rush over to the Guinness Storehouse at a certain time. Also, be aware that some of the things listed on the Dublin Pass website are free to the public without the pass.

Consider the Airlink Hop On Hop Off Return voucher, which you can buy online. The Airlink bus (737 or 747), which runs frequently, takes you from Dublin Airport to any number of stops in Dublin, one of which is likely within easy walking distance from where you are staying if you are staying down town. The Return voucher includes one ride from the airport to downtown and another within 90 days back to the airport. It also includes 48 hours Hop On Hop Off starting from the time the ticket is first validated on a Hop On Hop Off bus. It also includes the Paddy Liddy walking tour free. We reserved our Book of Kells ticket online for 10 AM (was first available that day) and Kilmainham Gaol 1:30 PM (only time available) for the same day. We took the first Hop On Hop Off bus from the GPO on O'Connell Street to Trinity College to see the Book of Kells exhibit (we could have walked and did get off the bus at an earlier stop than planned because AM Dublin traffic is gridlock). We had plenty of time after seeing the Book of Kells exhibit to take the Hop On Hop Off bus to Kilmainham Gaol and had a nice pub lunch just across from the jail while awaiting our start time. We then picked up the Hop On Hop Off bus to complete the circuit. On the second day (after getting a ticket from the bus driver the previous day), we went to the GPO and cut short our visit slightly to begin the 11 AM Paddy Liddy walking tour, which begins in front of the GPO. While we could have taken the Hop On Hop Off bus the second day (the drivers provide very good and entertaining narrative and none of them seem to like Temple Bar), we instead walked from the end of the walking tour to EPIC (the Emigration Museum). Overall we had two full days seeing the Book of Kells exhibit, Kilmainham Gaol, the GPO, EPIC, a worthwhile bus drive around Dublin including Phoenix Park and a very good walking tour. There is a lot of ancient and relatively recent Irish history that is very well presented with the above experiences and we would not have changed anything. We avoided Temple Bar (except for the walk through on the walking tour), avoided the Guiness Experience and Jameson Distillery (other things were higher priority, drank Guiness instead). If we had had a third full day we probably would have visited at least a couple of the churches and the Archaeology Museum. Get your Book of Kells and Kilmainham Gaol tickets online now if you haven't already and if you plan to visit those sites.