We have had success mixing the 2. We have 2 peacocks with a Jack Dempsey and also have 2 Bichirs with them. We used to have jewels, mbunas and yellow fin in the same tank too but I recently made a jewels only tank and the yellow fin found a new home. The mbunas were mean constantly so we gave them to our LFS buddy.
In my honest opinion, I prefer American/new world. As mentioned above, mbunas are mean little turds. I like my fish to interact not fight. I like peacocks too though.
But my FAVORITE is my Festae. Of course she has a tank to herself because I'm afraid she'll kill or hurt any other fish I may put in. I'm growing out my albino BN plecos and a crawfish so hopefully I can keep them with her as a clean up crew.
Sorry about my tangent...
In a nutshell, either mix or SA/CA
Happily married Mommy of 3 babies, 2 fur babies and 15 gilled babies