: With accepting the new Autumn comes new retcons. Is that OK too?

: It was canon that the Halcyon-class was the smallest UNSC ship to receive the
: designation of cruiser. While this was the Halo 1 version it was fine
: because the Marathon-class was larger.

: But now, the Reach version Autumn is larger than the Marathon-class.

The Marathon class came from where? Is it the one that gets energy beamed in the "What if you miss?" cutscene in Halo 2? And the reference to the Halcyon class' size came from The Fall of Reach I assume?

In my opinion what we're looking at here is references from a book who's material has largely either been superseded explicitly (Elites fighting throughout the entire Covenant war) or implicitly (like with the idea of UNSC ships having rotating sections for gravity which has never being mentioned ever again) and sizes and dimensions from a game (Halo 2) who's development was later revealed to be extremely rocky.

I like The Fall of Reach and I like Halo 2, but I very nearly don't consider the former canon anymore except for the parts that are supported by later fiction (Cody Miller, eat your heart out! :P) and am always cautious when relying on anything but the most direct facts from the later. Measuring in game ship sizes would not count as a most direct fact for instance.

: Another difference between the two is the Reach Autumn is only superficially
: different (in add-on details only) from the new Autumn-class. Yet one's a
: light cruiser and the other a heavy cruiser.

: These two data points can only really make sense if the actual Pillar of
: Autumn is still the Halo 1 style and the Autumn class looks mostly like
: the Reach style

The Autumn class are from where again? The cutscenes in Halo 4? The long version of the Halo 4 commercial with the christening of the UNSC Infinity? You may have a perfectly reasonable answer for this, but how do we even know how big those ships are or that they are heavy cruisers? If I (being the less detail oriented person that I am) tried to classify them I'd probably come up with the idea that they're all Halcyon class, just some that were refurbished from storage on some world not hit by the Covenant.

In any case I'd lament the fact that 343i chose to make a ship so visually similar to the Pillar of Autumn. If we go by Halo Wars the Autumn (and thus Halcyon class) is something around a forty year old design at best. Trying to explain and classify things that seem so similar is hard, and maybe a bit of ship design diversity would be good for Halo.

I believe in making up fiction to best fit what we have, and in this case our most solid facts tell us that the Pillar of Autumn (seen in Halo CE, various books, and Halo Reach) is a Halcyon class cruiser. Everything else, as far as I know, is less concrete and thus has to bend so as to fit around what we know about the Pillar of Autumn.