I have 6-7 nights alloted. Which has more to do, Sarlat or Limoges? Is 3 nights each too much? One extra night could be Limoge or Paris (have been before).
Sarlat, for sure. Be sure you have a car to visit the many sights in the Dordogne. I would allocate all my time to that area (not just in Sarlat).
Sarlat. But don't stay there. Get a car and stay in whatever excellent accommodation you find in that area. You don't say when you're going, but if it's this year, be sure to drive through Abjat-sur-Bandiat to see if the (synthetic) flower garlands are still up from the Felibree, which was about a month ago. If it's next year after, the festival will be in Brantome the first weekend in July.
I have never been to either. But Limoges in 'on my list" as it is the closest major town accessible by mass transit from elsewhere in France to Oradour-sur-Glane. Oradour-sur-Glane is the town effectively wiped out—along with all of her inhabitants—by the Nazis shortly after D-day. It was subsequently memorialized and kept in its preserved, ruined state by President De Gaulle to forever remind people of these atrocities. If for no other reason, this would be my choice. I hope to get there someday in the next couple of years.
Oradour-sur-Glane is very moving.
Well worth a visit.
We visited. Highly recommended.