Obviously, the cost to sequence a genome depends on its size. The discussion below is focused on the human genome; keep in mind that a single 'representative' copy of the human genome is ~3 billion bases in size, whereas a given person's actual (diploid) genome is ~6 billion bases in size.
Alternatively, EPA has a more beneficial effect on lowering overall LDL (bad) cholesterol. In the cognitive domain, DHA appears to offer greater mental benefits. DHA has been suggested to be more effective in improving overall cognition and preventing cognitive decline in healthy older adults.
DHA, in particular, is a type of omega-3 fat that's been found to boost brain function and even promote brain healing, although it's more plentiful in animal-based omega-3 sources, like krill and wild Alaskan salmon, as opposed to walnuts.