Depends on your area of course.
Burundi are everywhere, but being common does not mean you won't want them.
Nangu are not super common, but they are the most common Zambian import.
Also, those Burundi are most likely F1000's. The Nangu very well could be F1 or F2.
In my area with millions of Burundi being around, I'd figure $20 each when trying to sell one by one, and about $125 as a group deal.
Nangu, closer to $35 each, and $175 for the group.
In general you can make more money selling individual fish, but takes forever to move that way, that is why the math does not match up.
In short, value wise Nangu is worth more.
Nangu are less common in the industry.
Depends what you like to look at, Nangu are kind of like faded Mpimbwe, they have color, just not alot.
burundi have huge heads and bigger spawns.