TEPaul - Its been a while since I've played RCD & RP - a situation that I plan to remedy this summer - but as I recall, Portrush wouldn't lose a thing without its 18th. I agree that its a good hole but based on the absolute greatness of the preceding holes, Portrush would climb in the rankings as a 17 holer. In other words, the 18th is below average FOR PORTRUSH.
Maybe my terminology was misleading - when I said "really strong finishing holes" I meant holes that were above average for that course. Since I think the 18th at Portrush is below average FOR PORTRUSH - it certainly fails that criteria.
I'll give you County Down - you wouldn't want to take away the 18th there - but I'm still not sure it's ABOVE average for RCD, so is it a "strong finishing hole?" Along the same lines, you wouldn't want to take away the 18th at TOC. But is the 18th at TOC in the same class as the Road Hole? They are both worthy holes but they aren't the fantastic finishing holes you'd hope for.
I was just singling out Carnoustie & Muirfield as the unusual links courses that have finishing holes that are as good, if not better, than the other 17 on the course.