A good coticule is far more versatile than a BBW, and there's nothing it can not do that a BBW can. A good coti can cut at 3-8K level with the application of slurry, and polish above 8K level, so it's not even a question which I'd choose given the choice.
In a way its ALMOST like asking, would you rather have: a 3/8 combo Naniwa, or just a 5K?