there's been a debate on this topic already. i've imported fish just like the ones above with the spots and stripes, and i've kept pustulatus over 6 years ago already and fahaka, if you look in my picture thread, there are pictures and examples of both, and ones like you posted as well.
the SPECULATION is they're either:
hybrids of fahaka / pustulatus
geographical variations of either species
a 3rd species neither fahaka or pustulatus
or sexual dimorphism of either specie
if i get a chance, i'll try to dig up the old pictures of the ones i imported about 3 years ago. well, the ones i ended up selling about 10 pcs, to Oddball on this board, and he said they all grew up and turned out like regular fahakas.
However, I did receive a few pustulatus in the past, and one specimen outgrew all the rest and had stripes and spots on it, it was 12" when it died, but the rest in the group were heavily spotted, it seems that in pustulatus there are lots of variations.
Neither one of these are very closely related to tetradon mbu, nor their distribution.
Pustulatus have a very limited range where its found, but fahaka is widely distributed in the W. African rivers, and OVERLAPS pustulatus, and often mistaken for such from fisherman!!!