go with tanganyikans if you can find some. i have three tanks for the tanganyikans, imported a lot of it from across north america... there stunning. amazing shapes, colors, and personalitys. i dont like mbuna anymore because of tanganyika.
the main things to consider between mbuna and tanganyika..
mbuna : cheaper and more common.most mbuna share a common body shape, but differ in color. generally hardier then tanganyikans, but a lot of them are highly inbred and hybridized, so not very "realisic" if creating a natural biotope.
tanganyikans: more expensive, generally less colorfull but greater diversity in body shape and personality. harder to find (for me anyways) most can be found in F-1 and get a very realistic wild like fish.
both are highly entaining... it come down to choice.