I actually think its a little more complex than that. "Grand Strategy" is a genre that is terribly difficult to define; there are areas where ETW and EU3 can/should be compared (like campaign AI), and then there are areas that they shouldn't be compared (like military - eg I like your earlier point that EU3 simulates the
outcomes of wars and battles better than ETW, but as for the battles themselves, you really can't compare; it wouldn't be fair to EU3

).
But your analogy is a bit misleading - I think comparing two "Grand Strategy" games is more like comparing two "War" games. "War", as a genre, is uber-broad. It could refer to WWII shooters, WWII RTSs, etc. etc. However, you can still compare them, where comparisons are valid. You can't compare Call of Duty to Company of Heroes very well; but you
can compare aspects of certain other games in this manner. While I agree the "Apples and Oranges" argument is a massive over-simplification, it really needs to be taken into account. All Total War games have been turn-based, and EU3 is real-time. Those make for VASTLY different experiences. Same goes for having abstract vs. 3D battles. But that doesn't make the games incomparable, as I've already stated. Both have functioning Campaign/Diplomacy AIs, but clearly one is superior.
Also, for Humble Warrior: Yes, Empire has its ahistorical travesties, but so does EU3 (to the untrained eye, it would suggest that, for instance, Longbowmen were a widespread military tradition across the entirety of Europe). I'll agree, it is a MUCH more informative game (I've learned bundles just looking at the starting map!

), but you can learn plenty from Empire as well. I really don't think that it will ruin someone's informative experience if their chainshot flies 50 meters too far. Most people touching Empire probably have never had ANY prior knowledge of the era; even if the knowledge isn't perfect, I think the fact that their learning about it (and perhaps striking up the desire to pick up an actual book of history?) is a good thing. Ninja ropes, however, are an awful, awful thing.
