That's very true. :thumbup: Hard wood is hard on tools and muscles alike. You'll have a more difficult time cutting / splitting hard, close-grained woods, knotty woods, etc. no matter what method you're using (wedges, axe, maul, batonning).
On that note, I thought this was pretty neat: This dude with painted fingernails does battle with a pretty tough tree using wooden wedges and prevails in the end, but sweet jebus does he ever have to put some effort into it:
That did make me think of another consideration, though. I'd suggest that you're not likely at all to annihilate your axe/maul/wooden wedge if you run into a piece of wood with a knot in it. You are, however, more likely to chip the edge of most knives (even heavy duty style knives) if you run into the same knots during batoning.
See: That video of the RTAK II above. "...an epic failure, the blade could not handle another knot in wood and two large chucks come out of the blade!" (From the video description), or this video of the exact same thing happening to a CS Leatherneck.
Now, I recognize that both of these guys were dumb in that they should have realized they didn't have a chance in hell of slamming right directly through those knots with their knives (especially that second guy, sweet jebus..."if at first you don't succeed, hit it with a bigger stick"

), and that their dimness shouldn't be turned into an argument against batoning in general. You mentioned a similar situation where you just stopped batoning a difficult piece of wood - that's what these folks in the videos should have clued in and done. It is worth saying, though, that if they had they been using, say, a wooden wedge or something, a) the end result would have been the same (ie: They would have tried and failed to plough right through the middle of those knots), but b) They would not have destroyed their knives in the effort.