I have a modern french hammer-maul which is about 4 pound. It is quite "sharp" and it works usually, but no better than my other splitting axe (french antique) which is lighter, and blunt as my #### it alledgedly had steep secondary bevels (at one time)
. If the wood is tight with knots etc I'd rather the axe bounce out thangrab with a sharp edge and be a pain to have to remove (or do the slap down until it eventualley gives, waste of energy IMHO) if it get's stuck. I find if you try to "split" with a sharp edge the edge will try to cut through any fibres in it's way rather than just part them in one, and it takes more effort to shave your way through
Plus the axe need's to be fat-wedge shaped not slim profile like a chopping or felling axe. And aa sharp sharp edge wont stay that way for long spliting logs in any case (grit/mud etc on end grain) Keep the sharp sharp one for shaping and trimming, the blunt sharp one for splitting