I've gone through and played the campaign and the first three chapters of Spartan ops two or so times now, and one of the biggest things that I've noticed during some scenes is the size of some of the CCS-class Battlecruisers. While this Covenant warship has appeared in a majority of the previous games, its design was the major thing that has changed over the years. But strangely, the size of this vessel is altered in certain scenes throughout Halo 4.
In the first level, Dawn, the cruiser that was destroyed by the missile seemed quite smaller than the aft section of the Forward Unto Dawn, and even if the frigate was still in one piece, it would've been about a fifth of a cruiser's size.
The one or two times I can't complain about the cruiser's size is during the levels Forerunner and Infinity. In Forerunner, the cruiser that had deployed the drop pods actually seemed similar in size to previous cruisers featured in ODST and Reach. Then in Infinity, it almost seemed like the closest cruiser to the UNSC Infinity's crash site was a bit small, but that could've just been because it was a distance away from the ship.
Now, there was one scene that really started to bug me a bit after playing the level Reclaimer a couple times. Right after talking to the Librarian and moving through the portal, there's a cruiser flying by the battlefield as the Infinity moves into close view. The cruiser here just kept on moving closer towards Infinity, but the massive ship almost seemed like Godzilla to King Kong. Now, it could just be a regular cruiser or some other form of ship, but it just seemed strange for just a large covenant ship to be drastically dwarved by a human vessel, when the Infinity is supposed to be the length of over three battlecruisers lined up.
During the first cinematic video for Spartan Ops Episode 1, just before the Infinity exits Slipspace, there's a battlegroup of "speedy" cruisers and what appears to be an over-hauled and highly-detailed battlecruiser within the flotilla. This said cruiser is surprisingly larger than the other cruisers around but these could be two different class cruisers: judging from how large the ship was while being rammed by the Infinity, I can only guess that this ship was a CCS-class Battlecruiser while the others were ordinary Cruisers, and that these smaller cruisers seemed similar in size to the deployed and redisigned Charon-class Light Frigates (which I actually prefer over Halo 3's design).
There's no inconsistency its just two different classes of ship. The larger ones (such as the one in Ep. 1 of Spartan Ops) are indeed CCS-Class Battlecruisers, the smaller ones like the one destroyed in Dawn are CRS-Class Light Cruiser (which yes, have existed before Halo 4) which were described as outwardly similar in appearance but vastly smaller.