Driving from Dublin to Dingle, will leave Dublin around 9am so want to hit some sites along the way. Kilkenny Castle and the Rock of Cashel both seem to pop up - should we try to do both or is one better than the other? Or should we do something completely different? Looks like a straight drive from Dublin to Dingle is a 4 hour drive but we're fine to arrive in Dingle around 7pm give or take.
You'd have time to do both if you wanted. Kilkenny has much more to see and do though. Smithwick's Brewery is in Kilkenny. Try lunch at the Kytelers Inn with history dating back to 1263. If you go there be sure to check out the basement.
I don't know why you couldn't do both. I've been to both and if I had to choose one I would pick the Rock of Cashel.
The Rock of Cashel can be a fairly quick stop so depending on what you want to do in Kilkenny it could be a good place to stretch your legs for a couple hours. Both are about an hour apart so they won't affect your day too much to visit each place. I wouldn't add more though other than bathroom breaks, no reason to feel rushed that day.
We've done both on the same day and had plenty of time in each. Since you are ok with a late arrival in Dingle, you might as well get the most out of the drive. Go for it. TC
I don't know if this will alter your decision, but when I was at the Rock of Cashel in early June, much of it was covered with scaffolding. Now, I was still able to tour the castle, but the best picture taking opportunities were negatively effected.
Cashel is basically a ruin. Kilkenny is a restored Castle as is Cahir Castle which is near Cashel. All are different and worth a stop.