New Vegas in exploration is...
Well, cut down the dungeons from Skyrim about 90%.
The dungeons in FNV are small, some caves are even just two rooms.
The gameworld is also filled with invisible walls to guide you on the path for the main quest.
New Vegas isn't a exploration game. It's a roleplaying game. It's about dialogue, character interaction, questing, choices, AnC but not about exploration.
So if you want a sigh-seeing game for your sandbox needs then get Fallout 3 or Oblivion, but New Vegas is not like them. It's an RPG.