they should be shaving sharp imo. a sharp axe will save you time. also if an axe isn't sharp it can skip over the wood (and possibly into a leg or the ground) instead of biting into it.
old tree fellers would keep their axes extremely sharp and would even polish not just the edge but the whole cheek areas of the axe so to remove as much friction as possible so to make the axe more efficient.
an axe must not be fragile like a knife blade. the final angle is steep compared with a knife and may not feel as sharp but it will still shave easily.
of course there is no rule or laws, do your own thing but I think the sharper the better.
iv seen these argos axes and they are ok but nothing amazing, i just think that gransfors axes are a tad over rated and are the only comparison

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