Using a Dual point distributor... What is the benefit?

Dual points don't open exactly at the same time, but very close. In today's world almost any electronic distributor will provide better performance. And even an old single points distributor with an MSD 6AL box will give multi spark performance to work better than a dual point. This is the setup I use on the SBC in my '39 Chev and the old original single point distributor with MSD box works amazing.
Points are still limited to certain rpm ranges, so if you plan to run high rpm's expect any points distributor to begin to see point float around 6500 rpm's and then power will nose over. So high rpm's need a better electronic distributor to eliminate points float.

 

Which is why Mallory went to the four lobe cam. The points open half as often as a regular distributor with an eight lobe cam. This greatly reduces point float, so rev's can go up. Plus, since each point set has less work to do in more time, dwell can also be increased.