Discuss.
Honestly I preferred the atmosphere of New Vegas. The warfare between the different factions was great - Mr House, the NCR and the Legion as the big players, and then the smaller players being the Tribes and the Brotherhood. All the factions were well developed and interesting - especially the Boomers - loved them. The faction system was also amazing.
I also loved the fact that humanity was sort of rebuilding. There was conflict over power sources like the Helios Power Plant and the Hoover dam. The world felt desolate enough to still be a survival game but there was some sort of culture and civilisation about which was great. All the settlements made sense, with farms and water supplies and the bandits holed up in other places. The world felt like it was 200 years after the apocalypse because it was still post-apocalyptic but there was some sort of society developing and the conflicts arising from that was interesting.
FO3 was just eh in this regard. As a setting maybe 10-20 years after the bombs dropped, yeah it worked, but 200? No. The atmosphere was too oppressive and none of the settlements made sense. There was no interesting faction warfare between the towns and settlements and bigger factions like the Encalve and the Brotherhood - everything was too weird and isolated from each other and way too green and it didn't grab me as much as New Vegas did.
Also the subway system SUCKED.
That's why I want FO4 to take after NV more.