david weaver
I wouldn't recommend any of those for someone who is going to do a serious amount of hand tool work. PSA paper is better for back flattening, crystolon stones are better for bevel grinding, and natural stones are better and faster with less maintenance for honing.

Any steel that benefits from diamonds significantly is something that makes little practical sense for woodworking, but it sounds good on a forum to talk about steel that can last x times as long in a machine.

Metalwork and factory production are a different story, but we don't use those. there is some merit to diamond hones for touching up router bits, but use of router bits tends to result in bland-looking woodwork (my cabinet doors and a cove on an old piece of casework that I made are good examples of that - it's not like I need a diamond hone for those things, either - sending them out to be sharpened is probably more practical).

Diamonds are quite nice for cleaning a watch face, too, I guess, but most of the consumer plates aren't up to it.

Honing films are a waste of time. I've been down that road. I could be convinced of their usefulness for a guy who hones once every two months (they're cheap), but they are a step backwards vs. decent stones.