Dual-point vs. Single-point distributors - pros and cons?

Yep, longer dwell keeps the spark hot at higher rpms, single point units can fade as the rpms climb. Usually not an issue in day to day commuter cars, but is why you'll see them (factory) in rev-happy Commandos, 340s and other hipo engines of the day.
Cons are that good replacement parts are getting tough to find. (Big surprise there!)