This is what I don't understand, I thought it was a joke, and kinda funny, so I wasn't gonna say anything.
Hm... I dunno. Those beach shots don't look particularly different in the low quality comparisons. The lighting is different, but it doesn't look necessarily better. The textures on the sand actually look more detailed in the Halo 2 side. The close-up of the warhog has very little different being shown besides the viewscreen on the sniper rifle.
The interior building shots have better geometry and the lighting is better contrasted there. That's a step-up, but of course, it's a moot comparison for a map that was never meant to be shown...