My wife and I will be driving from Dublin to Ballycastle where we will stay for a few days. Wondering if we should just drive the straight route to Ballycastle or get off before Belfast and make our way around Dundrum, Downpatrick, etc. around the coast then back towards Ballycastle.
What day of the week? What sorts of things are you interested in doing and seeing along the way? How long do you want the drive to take? Everyone is different and there is no "one size fits all" answer.
Personally, I like driving the back roads. Seeing what REAL Ireland is like. Not just the M1. But, if you're skiddish about driving where there is barely enough room for you and another car ... or afraid of getting lost. I'd stick to the M1. :)
The Down coast does not have the WOW factor of the Antrim coast. It is gentler and mostly at sea level. Co. Down has a lot to offer but for those who will spend some time there. I am particularly fond of the Ards Peninsula and Mount Stewart. Many houses, gardens, etc. are not open on weekdays in NI in off-season.
You may be better off going directly to Ballycastle. Depending on your route you could stop off at Hillsborough for lunch. What a lovely town! There is a fort and park in back of town, a beautiful church and Hillsborough Castle (since it is an official royal residence opening times are hit or miss).