For me, perhaps the most interesting thing was seeing how AOTCR used to be. At around 2:52 (in any of the vids, but try the one with O'Donnell and Staten - here for 480p), an Elite can be seen running for a Banshee in the LZ. Then MC is approaching one himself, except it seems to be on the side you land on.

Then he's flying a Banshee in the first snowfield, and I wonder where it came from. I don't imagine it would've been from the LZ, unless the level had a different arrangement allowing simple access (you wouldn't expect players to be squeezing it through the first room). So I'm guessing it was somewhere in that field.

Around 4:20 MC emerges there, and an Elite is just ahead, which is different of course. Another difference is the very pointy rock on the left - and later there's another pointy one. Evidently the rock geometry got tamed somewhat for the final game. Perhaps so rocks could more readily be used as perches - that would be my guess.

In regard to the covie dropship landing in the first snowfield, that's something seen in the game's show footage which plays when you leave the main menu idle for a while, so I was already familiar with seeing that difference. Interestingly, this one drops two manned Ghosts. In H1 Ghosts do arrive by dropship in the later area with the huge tower, but they're initially empty. I wonder why Bungie decided against having them already manned.

The Scorpion initially looks broken - something remarked on by O'Donnell at 5:55. Seem weird. I'm wondering if it was merely on a rock, which it then drives off. Hard to tell.

One very minor thing. In the boarding prompt the game writes 'ghost', whereas H1 writes 'Ghost'.

Another little point of terminology. At 0:36 you see "autosaving… done". Apparently it was only later that they rephrased things to have the term 'checkpoint'.