In my opinion the two shows are similar in some respects and very different in others. RAP, from its inception early on taking place in a backyard, has always been a frag swap with some manufacturers thrown in for good measure. Granted it is a frag swap on steroids, but I believe that emphasis is definitely on folks selling frags and fish. MACNA definitely has its share of exhibitors selling frags, but the emphasis is more on education. Now I know that RAP does have some speakers, but MACNA averages anywhere from 24 to 30 speakers over the course of 3 days. The exhibit hall is much larger and has a lot of the top manufacturers as exhibitors. You can meet the designers face to face and talk to them about their products and future plans for updates and improvements.
Since I live in San Diego, I have the pleasure of being able to attend RAP here in SoCal. I go every year. I also go to MACNA. Two different yet similar shows. There is no reason to not go to both. :)