Can do 2 out of 4

I only managed two of the four, Slea Head, and a day trip to Inishmore. Loved both. I don’t think you can go wrong with any of them. Just pick what fits best with the rest of your schedule.

I would suggest you look at all four and decide what you’re most interested in seeing. What interests me might not be of interest to you and I’ve been to all four.

I managed to do 3 of the four: Ring of Kerry, Great Blasket Island, and Inis Mor ("Aran Island"). I spent two nights on Inis Mor (loved it). But I also added the best one of all: Skellig Michael. Great Blasket Island was incredibly awesome, but I'd trade that (and the ROK) away for Skellig Michael.

When is your trip and how many days? Time of year and weather can be major determining factors.

The most incredible, memorable and favorite places on my trip to Ireland were: Skellig Michael, Inis Mor and Great Blasket Island (in that order). We skipped a lot of other places that I have no doubt would also have been awesome, but was glad we managed to get to these very special places.

Are you going to be doing the driving? That will affect what you can see while you’re watching the road, although you can pull off for views as you progress. Also, if you don’t include Blasket Island or the Slea Head Loop, will you still be visiting Dingle and the Dingle Peninsula anyway? The town and surrounding area are a delight.

Having to pick just two, I’d suggest Aran Island (the biggest, Inishmore, although our ferry from Inishmore to the mainland south of Doolin also stopped off for an hour at the smallest, Inisheer), and Ring of Kerry.

A couple of notes: In 2011, staying in a cottage outside of Dingle that’s no longer being rented, I bicycled the Slea Head loop, but did not take a ferry to Great Blasket Island. That was done in a day.

We drove the Ring of Kerry in 2023 (my husband did the driving), and took two days, staying overnight in Glenbeigh.

Also, visiting Inishmore twice, on two trips, we took ferries once and flew the second time, on the small Aer Arran plane. Unless you’re bringing a bicycle, where the ferry has room, go with the plane, whose schedule isn’t as affected by weather and rough seas as the ferry, which can get canceled.

I have only done two of four: Driving Slea Head and Aran Island (Inishmore). Both were great. Blasket Island is right on the Slea Head loop drive, and perhaps you could add it in along the way?
Ultimately, and others have stated, it depends on the rest of your trip. Are these four the only things that you will be doing. If so, I would couple Dingle Peninsula (Slea Head and Blasket Island) with Aran Islands since they are closer.