Which one is more scenic? Dublin to Paris or Dublin to London

Neither of these journeys could be considered scenic. What exactly are you attempting to achieve?

From Dublin you're looking at flying either way - ferry/train wouldn't be particularly efficient to London and would be an absolute ordeal trying to get to Paris.

Are you planning to spend time in Ireland, or are you just going to be landing in Dublin because you're flying Aer Lingus? If the latter, it's very easy to get connecting flights to either London or Paris. You should book it all on one ticket so you can check your luggage through to your final destination and in case your transatlantic flight is delayed, you'll be protected (not lose what you paid for your connecting flight).

The water on both ferries will be similar.

I saw on one website that Lon-Dub, you could at least see an abandoned castle; and the longest named station in England. I just thought that since we have never traveled through train or ferry here in the US, it's also a good experience to do it when we travel in Europe. In one of our trips, we're actually taking the plane. We want to try at least one of the ways to or from Dublin the train/ferry trip.

We're not checking any bags. The 3 cities in our Europe trip are: London, Paris, and Dublin.

I was curious about a Dublin to "Paris" ferry and found a Dublin to Cherbourg sailing that operates one time a week. The sailing take 18 hours 55 minutes, then you'd have to get a train to Paris ( 3+ hours). Since it just goes once a week if it's cancelled for rough seas you'll be out of luck.

https://www.directferries.ie/dublin_cherbourg_ferry.htm

If you want to experience train travel then consider taking the Eurostar from London to Paris. It goes under the English Channel and only takes a couple of hours.

How many days do you have? The ferry from Dublin lands in Wales then you take a train to London. You can easily take trains from London to various places for a day trip including several castles that are still lived in. Windsor Castle is a good 3/4 of a day visit from Central London.

I expect the train goes via LanfairPG, Wales for the long name thing.

https://en.wikipedia.org/wiki/Llanfairpwll_railway_station

This is a good info. Thank you!

The 1 time a week though is probably not going to be a good choice for us. We're only going to be in Dublin for a day. This trip is not really meant to experience a "lot" this first year we are travelling. I just want to know possible options for a "short/relaxed" vacation. Our main city is Paris, because our cousin lives there. Then we added the London and Dublin as side trips. We know that 9 days will not be enough, but better than not going (we think).

From my own research, it seems like the London-Paris train is probably the best "train ride" we should try. If we do the ferry, then Holyhead & Ulysses to Dublin. I guess it's best to fly out of Dublin whether to London or Paris.

Thanks everyone!!!

You didn't give the month of the trip. It might be good to give a sketch of the itinerary, and the total number of nights you'll be sleeping in Europe/UK/Ireland. I would think a ferry ride could be more likely to be seasick inducing during the winter. Honestly, I think your time is too valuable to be spent investigating obsolete modes of travel. You need to understand that no one is being unsympathetic to you, but since there are two ferries and two trains between Dublin and Paris, you seem to have a romantic ideal that isn't very practical.

You might start with our host's general tips (blue menu top left.) But I looked and it's not immediately obvious from his hints that taking ferries between Dublin and Paris would not be a good idea. There are also issues of cost and bag handling, as well as your valuable vacation time. "Brexit" could also have possible bad effects on the plan. As it is, British immigration has always given my U.S.-born, 100% Americanski (Protestant, at that!) wife a hard time on arriving from Ireland because of her middle name. They are certain she is coming to take someone's job away.

Even if you want to consider it, you should investigate getting from your Dublin hotel to the ferry, and how many trains, and how much they will cost to get to London. Your OP Subject Line suggests that you aren't really planning to see London right now. Is that right? Honestly, with the uncertainty of Brexit, you might be better off leaving London for another time. But if you have particular objectives in England or London, my advice there is not worth much.

It is true that most train rides are more scenic than most corresponding car rides. But "scenic" is a relative term. I can tell you that the Eurostar train from London to Paris isn't very "scenic". We take trains all the time. But (see Rick's hints) the relaxing nature of the trip, and starting and ending in the middle of a city center is a big plus.

It wouldn't be this time. But we're in the process of looking at flights already, and might buy this week.

I'm appreciative of all your direct answers. It's confusing, because as you have said, "scenic" or "enjoyable" are relative. Some people have commented that the amount of time we might spend at the airport (considering delayed or cancelled flights when it's foggy or the crowd around late Spring to early Summer) could be a hassle, too; compared to the frequency of train arrivals/departures. That's why we considered the idea of maybe trying the train, too.

It's really good that you mentioned the Dublin port from where we are planning to stay. So far, we're looking into staying near the airport. Maybe a 15-20 min drive? I haven't looked into where the port is going to be, so thank you! I just entertained the idea last night, so I haven't looked at the distance from our accommodation to the ferry.

Keep those info coming! Really learning a lot!!!

3 days in London, Weekend in Paris, 1 day in Dublin. We have the option to arrive in Dublin instead of London, but weekend should definitely be in Paris; because our cousin wants to be able to join us on those days going around.

So you're now planning to fly into London, spend 3 days there, go to Paris for the weekend, then go to Dublin for a day and fly home? That sounds like a workable plan.

You can take the Eurostar from London to Paris and thus fulfill your ferry wish. Be aware that the ticket prices go up the nearer to your travel date, so your best bargain is to buy ahead. Since you'd be scheduled to land in London 3 days prior, a flight delay would not prevent you from catching your intended Eurostar.

Then, after the weekend with your cousin, fly from Paris to Dublin. If possible, buy this leg on the same ticket as your transatlantic flights so that if somehow your Paris departure were badly delayed, you'd still be protected and not lose your Dublin-USA cost.

Thanks everyone for the info!

You can take the Eurostar from London to Paris and thus fulfill your ferry wish.

What? This train goes through a rather famous tunnel under the English Channel.

Before I started looking for any remaining "Boat Trains", I would search this newsboard for "channel ferry sick":
https://search.ricksteves.com/?utf8=%E2%9C%93&query=channel+ferry+sick&button=
But I suspect you have to walk on to the ferry, with yet more baggage handling. Like I wrote before, "romantic" ideal.

Update:
We're not going to Dublin anymore (at least this year). All your inputs were very helpful! We realized that Dublin should be more of a planned trip rather than a side trip. It's that "first-time-in-Europe-gotta-go-to-many-countries" vibe we were on. Even though before we bought our tickets, we agreed that we should go again next year; so no worries of doing everything! We'll enjoy London a bit more before we see our cousin in Paris.

Thanks again!