For something being SUPER EASY to perform seems like an advantage to me... If this edge geometry allows people with little or no sharpening equipment or skills to get a nice sharp edge... what is the problem with it?
The problem is convex edges cut poorly. I have seen them all, including professionally applied re-grinds to a zero edge on a full height flat grind, and they all cut poorly. For chopping they are much closer to a V edge, especially on a heavy knife, or against a thick V-edge on a Full Flat Grind, but with matching thicknesses where it matters, they still tend to be inferior.
Probably the only thing a convex edge does better, when done full height on a Full Flat Grind, is what it was initially intended to do by Bill Moran when he introduced the idea on knives: Cutting free-hanging 1" manila rope...
That is why they should be properly called Moran edges, which is what they were called back then. I know the Japanese were using similar edges for centuries, but they had to give some rigidity to a very flexible edge in battle... Moran really introduced the concept for knife use.
Convex edges also might split wood grain-wise better, but that can hardly be called cutting...
The worst thing about them is that, to give an initial impression of performance, they depend heavily on a pristine and highly polished apex, which is quickly gone. So not only do they cut poorly most materials, especially meat, they lose that limited cutting ability quicker.
They add more material on the edge
exactly where you want to remove it... Modern steels that are correctly done, and not damaged at the edge by power tools, as many knives are, do not need that much support.
For crappy steel prone to micro-folds, I can see how the this edge design might fudge the issue, and seem to perform better in edge durability...
Besides, even those with the best motor skills... are nowhere near a constant angle while sharpening freehand... We are no milling machines. Somewhere I read that, whether we like it or not, sharpening on a benchstone will always produce convex edges (to some extent).
Not really true if you sharpen lengthwise parallel to the edge, with a very slight diagonal. All of my hand-applied edges look as if they were machine-milled edges, even down to the regular spacing and parallelism of the very obvious striations, but with an odd diagonal grain that gives them away as not machine-made... And that is how you want them to look.
The other difference is that a truly power-applied edge will sometimes, not always, degrade the apex cohesion, which is obviously not the case with hand-applied edges...
My trick is to use worn Extra-Coarse Dia-Sharp diamond hones (not fresh ones), which unlike stones remain perfectly flat, and to use lengthwise strokes, only barely diagonal, to limit side-to-side rocking. A diagonal movement prevents the coarse striations from weakening the apex by being parallel to it, and these diagonal striations can also create a bit of "teeths" on the apex.
Finishing over that, with a medium stone, working only on the final edge apex, must be as minimal as possible, and mostly intended to remove any remaining wire edge portions. The worn Extra-Coarse striations should show evenly in a diagonal throughout the bevel, reaching as close as possible to the final apex.
The overall bevel angle for chopping wood should be around 10-12 degrees per side (20-24 inclusive). Compared to the ususal 15-20 degrees per side (30-40 inclusive) that is usually used for chopping, the difference in wood can easily be felt in the hand from the more gradual deceleration: Even on Youtube video, you can see a lot of Busse used for chopping making that pat-pat sound, with slow progress that is really painful to watch...
But the biggest difference is of course in slicing performance. The only way 20 degree per side edges remain in use -a mind-boggling forty degree wedge- is that people only test by shaving hairs or cutting paper, or assume from poor knives that they can't hold the edge angle any thinner... And it is true: Most knives can't, in most cases probably because of the extensive use of power tools on the edge finish...
Gaston
