Actually, there is a difference. There are technically two different species, C. frontosa, whether six stripe (what most people call Burundi) or seven stripe (Kigoma) and then C. gibberosa, Moba, Mpimbwe, etc. Gibberosa tend to have smaller, slower growing humps. Some gibberosa ultimately develop pretty large humps, but many to most, including big males, don't develop quite the same huge, bulbous humps you see in a lot of big frontosa. On average frontosa have the more exaggerated humps.
The trade off is that gibberosa are generally more blue, often much more blue, which is why they're more expensive. Same deal here, doesn't mean there aren't some very blue frontosa, especially collected from certain locations, but all in all gibberosa are generally better color and price reflects that.