The problem with historical accuracy, especially in this era, is that the Great Powers only ever got into a serious knock-down, drag-out, life-and-death fight ONCE, and during that time, the French had one of the greatest military commanders in history on their side.
You can't really say, with absolute certainty, that any of the great powers were 'better' than the others. In their previous conflicts, one side usually surrendered when the other gained enough allies.

The same can be said of individual units. The Old Guard are talked about extensively, and highly regarded, but they rarely saw battle when compared to the Russian Lieb Guard.
Sure, the Old Guard won a higher percentage of their battles than the Russian Life Guards, but they usually weren't committed unless A) Napoleon was present and B) Victory was already likely.
While B indicates more intelligence on the part of their commander, perhaps, it doesn't really indicate that the Old Guard was superior in a straight-up fight. Since the two never met in combat, its all speculation.

Hence, 'historical accuracy' would be based on opinions. Which would, in turn, be based on the opinions of people at the time. Which would probably be based on the opinions of military commanders of the era.