Kevin -
This same topic was discussed here within the past 3-6 months and has been discussed at other times over the past several years. Maybe someone can find the most recent thread and link it to this one.
I think the consensus is that Ireland edges Scotland in terms of top-5 or top-10 courses. However, Scotland is WAY ahead of Scotland in terms of number of worthwhile courses and their density & proximity to each other.
The problem is that 5 or 10 ten best courses in Ireland are pretty much spread all around the coastline of the Ireland. It can take you 2 or 3 hours (or more) to drive from one to the next one. These courses rarely have any other real good courses near to them.
If you are looking for a place where you can plant yourself for a week in the same B&B or hotel and play 1 or 2 great courses and another 2 or 3 really good courses without having to drive more than 30 or 45 minutes (or an hour, tops) in any direction, Scotland has several areas that offer that kind of situation.
East Lotian in Scotland has Muirfield, Gullan, North Berwick, Dunbar and others. Fife has all the courses at St. Andrews, Crail, Kingsbarns, Elie, etc. The Highlands has Royal Dornoch, Nairn, Brora, Golspie, Tain & Fortrose. The Aberdeen area has Cruden Bay, Royal Aberdeen, Murcar, Peterhead & Stonehaven.
Don't forget about England! The Lancashire coastline from Hoylake to Lytham-St. Annes could be the best 75 mile stretch of golf in the world - Birkdale, Hillside, Formby, West Lancs, SouthportAinsdale, Hoylake and Lytham-St.Annes. If you stay in Southport, none of those courses are more than 40 miles away.
DT