NA/Naranon started after AA/Al-Anon. I assumed, especially after having been in Al-Anon for a long time and doing volunteering at the group rep and state convention level, that NA/Naranon was created because old-timers in AA were not comfortable with anything but alcohol addiction. I've heard old-timers talk about how when they were young, if their siblings got involved in illegal drugs, they would beat the heck out of them - even though they themselves were hugely into alcohol!! Illegal drugs were a huge taboo even in the drinking community. I wish that were still the case.
Nowadays it is hard to come across anyone who just is addicted to alcohol. I'm thinking that as the years go by there will not be much difference between the two programs. I gotta say, though, that while at an Alanon meeting I feel uncomfortable talking about my son's use of illegal drugs and the fears/worries that I have that go with the illegal aspect of it.