I've not done much cutting with my hook (a 5) but I do know some people who did a bunch of testing and training with hooks of various types. It seems like its half technique (cut on the diagonal) and half sharpness. In general, it seems like a good compromise to get something smaller than shears, and which may be easier to handle in certain situations, but expect to touch it up after every use (or "session") For what its worth, its a good idea if you need it, but of everyone I know who's done everything from high angle rescue to vehicle extraction, with hooks handy, very few actually used them "in anger", and even then, they could have used something else if they hadn't had the hook.
For me, it seems like a good thing to have if you have a kit or rig that needs a safe cutter, but shears would be too big, and a round-nosed knife would be otherwise redundant or against policy. For example, I do know a few people who carry Z-Rexs or gerber zips because they will cut 12mm rope, and they work at venues that restrict the carry of knives by policy. And if you work ropes, you need some form of cutter, full stop. Deployment and grip are going to be major factors. Can you keep hold of the hook and something else at the same time? Gloves, dexterity, etc.
While "cheap" cutters do not work as well, if the idea is to have the cutter available for self-rescue, then its likely that more cutters could be in more places, than for the cost of the benchmades. (And more willingness to conduct destructive training)
However, again, if I thought I would need a cutter in a particular role, I'd not hesitate to add one to a chest rig, or duty belt. Fine motor control can really go to pot fast sometimes. Really depends on the situational requirements. For example, my 5-hook is in my bigger hiking FAK because its lighter than shears, will do the job of clearing clothing in the case of snakebite or something else, and my SAK or whatever knife I have can handle tape and bandage duty quite well. I could use the knife to clear a pant-leg, but the hook would be more comforting for the patient, or if I'm self-treating, means I have less chance of doing further harm to myself.
Hope some of that helps.
edit: sharpening could be done with green compound on the right diameter rope or paracord, or on a more accurately sized dowel. Fine sandpaper could also be used with the dowel.