I'm the guy who'se never sharpened a razor yet, and uses coticules nearly every day.
Most of what I sharpen is kitchen cutlery, coming off a King 1200 for the initial shaping, and then a blue Aoto. Larger knives go from that to a BBW, and the smaller ones get some time on the Finnish stone, which is slightly finer and a fair bit harder..one of my favorite stones for all that it's a mid-grade.
It isn't as fast as a BBW, but has excellent 'feel', and produces a great working edge (with slurry). The reason I don't use the larger knives on it is strictly size. I've got an 8x3 BBW, but the Finnish stone is only 7x1.5 or so.
I'm a little inhibited using a rock that small for 10-14" blades, and in fact intend to get a larger BBW to accomodate them more easily.
I use the coticules minimally, as not all of my knives require (or can benefit from) that degree of polish, and I have various other polishing stones in
rotation. I have a uber-fine grained 'surgical steel' Case XX boning knife that gets the full monty, finishing on an 8x2 coticule, and several thin Japanese style mini-santoku utility/paring knives (about Rc 62 imo) that respond well.
What I won't bother with is softer 'simple' steel, anything below (guessing) Rc 56-58, as they won't hold the edge long enough to gain much.
And I have used the BBW on a 4x2 combo as a substitute grinder, reprofiling Most Tediously a 10" D2 blade from a short bevel to a long convex. It worked better than the DMT 1200 grit, leaving minimal scratches and a good beginning for a mirror polish. Others may have differing experiences, but I find the garnets in the BBW are not as even in size as the coticules. In that particular BBW there's occasionally an oversize speck of garnet that has to be lapped off or 'dug out'.]
The coticules garnets seem to be both smaller, and more consistent in size. For my personal taste, I'm inclined to save it for very fine grained steel, as that seems proper. I've also done craft (exacto knife) blades on coticule, and touched up surgeons needles (sewing, not injection) which I'll hasten to say were 100 year old vintage, nothing contemporary.
There are certainly big knives that are fine grained enough to benefit from polishing on a coticule, but I don't own them. Mine are nearly all mid-20th century vintage, mil-spec and similar, and they just aren't of the quality that requires coticules. I finish them on a Honsuita of about 6000 grit, and the fact they're soft(ish) compared to the best modern knives isn't so obvious. The stone is also (softish), compared to Belgians.