How do the SW Ireland peninsulas compare to West/NW Ireland coast?

Not crazy at all....Just because everyone says these are the must sees doesn't necessarily make them so. If you really want to avoiud crowds then AVOID kerry, Dingle and Cliffs of Moher. Ring of Beara is less busy but is rapidly catching up as the tourists have now latched onto it.

Mayo, Sligo and especially Donegal have some superb scenery but without the crowds you will see in the SW. The Ceide Cliffs in Mayo are 600" tall (compared with Moher at 700') but chances are you will have thenm to yourselves. They are also close to Ceide Fields which at 6000 years is the oldest known field system in the world (and possibly also the largest. Only a small fraction has been incovered and no one really knows how much is still hidden underneath the peat. It is a facinating place.

Donegal has Slieve League Cliffs which are among the highest and most spectacular sea cliffs in Europe, towering nearly 2000'
above the Atlantic. Have a look at this short video made in 2024. There's a bit more information here.

he rest of Donegal is equally as impressive with serious mountains, small viillages and sandy beaches. Go and discover the Rosguill Peninsula to see what I mean....

Be different and head to the NW - it definitely isn't crazy!

Crowding is a problem all over Ireland, and it's not just us Americans, although we do tend to stick out.

The NW is definitely less crowded. The spots Wasleys mentioned are all good candidates. I'd go farther in discouraging Moher - in June it will be mobbed with tour buses. If you must visit and it can't be by boat, maybe park at one end of the Moher Way and approach on foot. There are some closed areas on the path, so research it a bit. We did it by boat from Doolin. Doolin is crowded as well, but we'll put up with it for the excellent music.

Dunfanaghy, Belmullet, Achill are all less visited. We plan to visit Tory, Clare, and Inishbofin islands next Spring for overnight stays, and there's basically little to do but hike and an evening in the pub - our two favorite things.

Given your particular interests I agree that the NW would be the preferred direction to go, maybe to include an overnighter on Inishmore before heading north from Galway into Connemara and beyond as described by wasleys. I'd also put in a plug for Northern Ireland if you have the time and the interest. The Antrim Coast north of Belfast is worth the detour all by itself.
Regarding the summer crowds: we've always found the best way to enjoy the popular locations is to get an early start, ie well before the tour buses start to clog things up around 10 AM or so. We're early risers anyway so that strategy has always served us well.

All good advice above. I just want to add a couple points.
With a car, you can stay anywhere, so rather than identify a town to stay in, set the map wide on your preferred booking site, filter for your needs and budget, make a list of favorites, and mix it up. That said, I will say that I really enjoyed my stay in Killybegs, which gives you access to the Slieve League by both land and sea.
I wouldn't venture south of Newport. You can easily fill two weeks in Mayo, Sligo and Donegal alone. And you won't see huge crowds once you leave the airport.
For your next trip, focus on Northern Ireland, the Mourne and Sperrins Mountains, the Antrim Coast and Glens.
Have a great trip!

Already, these four replies are so helpful and relieving! Thank you so much!

(And others welcome to add!!)

If you decide on the Aran Islands, make it an overnight. The character changes as the last ferry full of day-trippers leaves.

Just as a reference, our next three week trip is (arrive DUB)-2xBelfast-2xCushendall-2xLetterkenny-Tory-2xSligo-2xClare Island-2xBelmullet-Inishbofin-2xCong-2xCavan-Trim-(depart DUB). We've already spent time in Belfast, Dunfanaghy, Donegal, Westport, and Clifden. Achill missed the cut. Trad music sessions are a biggie for us, so we tend to stay within a walk of a likely pub. The above itinerary yields 16 nights of music if it starts on the correct day of the week. And Belfast is our only repeat stay.

@jjgurley - thank you! The two weeks before the itinerary we are planning are in Ireland with a touring choir that I direct. We'll be excited to take in so much music as well! In fact, we will even be singing at the Trad on the Proms! We're also staying out on Inishbofin for a night at Murrays Hotel. We got connected to Andrew, the owner, who is a former singer with De Dannan and I understand that a lot of great musicians just find themselves there quite often! Can't wait!

We've never been to Trad on the Prom, but that's quite an honor to participate! We always have a drink at The Crane Bar, and the next thing we know is it's closing time and the players are packing up. Enjoy your trip.

If you do stumble on some sessions, google "Irish session etiquette" before you just start singing!

Another vote here for adding the Antrim coast - I’m so glad we didn’t miss Northern Ireland! Gorgeous and full of history, interesting to compare/contrast to the Republic.

Hi Jennifer! I do not think it's crazy to forego the SW of Ireland this trip. You could easily drive up from Galway to Co. Donegal via the WaW and see so much in 2 weeks. In my opinion, Co. Donegal is the hidden gem of Ireland--so beautiful! There is much to do outdoors, people are friendly, not too touristy even in June. While nature can be enjoyed throughout Ireland, I find the NW to be overflowing with natural beauty. And late June to early July is usually the weather "sweet spot" for Ireland. I hope you enjoy your visit! Sláinte!