Niall
Its hard to judge between the two so they must be somewhat similar. That said I think Ren is probably a bit tighter around greens with bunkering, but Dun has more raised greens where a slight error results in balls slinging off the wings. All in all I think Ren is slightly tougher for recoveries but that is probably down to better turf and faster greens as much as anything. But, each course has a good mixture of greens and surrounds.
Dundonald didn't exactly impress me, but it is good golf, generally with some room to miss and a few highlights such as 6 and 16. For me, the course is held back by too much water and too many sharpish doglegs. However, I suspect the property called for more doglegs because while the course felt spacious there isn't that much room if getting two loops back to the house was a priority. The club should really consider offering 9 hole rates.
Ciao