The multi-directional expansion created by hollow conical metal wedges ought to be the "cat's meow". Except for the prospect of trying to remove them at a later date without ruining the haft. That's the rub with that technique.
Usually I drill a hole thru the wedge slightly below its hammering surface.
It allows purchase of a pick or awl to dig it back out after everything has loosened.
Of course, thats years away, & basically 'my little secret' that a next guy wont know until its discovered the hard way.