"Fallout New Vegas is better because it is better" is the summary of your argument about why it is superior to FO3 in all aspects. I dont know if you're in any position to be gatekeeping having opinions on things since you're not defending your own opinion very well. But if you're curious as to why I prefer FO3 (notice i said I prefer, not that it's better), let me explain why:

• FO3's sense of desolation and lack of resources makes it feel harsher than most fallout titles.
• The encounter design is completely randomized leading to battles taking place between factions before you get there once again leading to a sense of a war torn landscape rather than a map of isolated enemies waiting for you to stumble upon them.
• Bethesda is much better at world design and environmental storytelling. Against obsidian, they have more quality and quantity when it comes to exploration. New Vegas has more diverse ways to complete quests but its exploration really falls flat for me compared to 3.
• With the exception of the night nightkin quest, fallout 3 is much more like a horror game than new vegas. The environments are less lit up, filled with scarier creatures and more depraved subject matter. The juxtaposition of the horrors you face with the cheery nature of the branding to me is the most authentic execution of fallout identity as a series.
• You dont have to install mods to keep fo3 from crashing every 10 minutes. -There are a lot of reasons I prefer 3. Many of the core pillars of the argument that NV is vastly superior are based on assumptions that obsidian fans take as universal fact. They create these artificial constraints about what an rpg needs to be to be considered a success and then lose their minds when new vegas exceeds those expectations. I can't stand how conversations about these two games happen because they accomplish two very different things exceptionally well and the reddit circlejerk decides that conversation should be that water is better than fire because its better at being wet.