Non-Euclidean :
The "largest landmass Bethseda Game Studios has ever created for post-release content."
That's big.
I thought some of the FNV content was huge. Zion was lovely and Lonesome Road seemed pretty big, but it was more linear.
I like Fallout New Vegas so much more than Fallout 4 so far, mostly for that spawning and quest issue. The game world is so huge, that you are never going to finish searching every crack in it, or get through all of the stories. I feel like Bethesda knew that before, and that is why expansions in Fallout 3 and Fallout New Vegas were much more focused. They were a more linear story to give you a break from the more repetitive aspects of the game and the huge landmass you had to explore already. Fallout New Vegas felt like it did this best, thanks to the different factions. There was a lot more involvement you could take in the main story line of the game.
In Fallout 4, there is the main story of finding Shaun, but the world is so massive, I feel there is no point in scavenging a building that will reload everything later, or completing a quest I will need to do again. How can I ever feel that I have done all there is in an area if I will need to do it all over again? This turns the excitement of exploration into a chore. And as the special items respawn too, it devalues them. Your in game actions feel kinda pointless.