The Brittany's 5/5 trainability comes from what it was built for. A pointing dog works at range, has to check in constantly, take direction at distance and hold position under pressure. Cooperation is not a nicety in that job; it is the job.
The practical result is a dog that is easy to teach, wants the feedback, and finds training rewarding in itself. Brittanys do well in obedience, agility, scent work and, obviously, field work.
The Akita's 3/5 is not slowness. It is independence. Guardian breeds were selected to act without a handler present, and the Akita understands a request, considers it, and arrives at a position. Positive, consistent, early work succeeds. Heavy-handed correction of a hundred-pound dog does not, and is unwise for reasons that need no explanation.
What the Akita most needs is not obedience but socialisation, sustained from eight weeks well past two years — because its dog-intolerance usually appears at social maturity, not in puppyhood.