It seems to me like the New Vegas map is much smaller than Fallout 3's map or is it just that NV showed a ton of unreachable areas on the map for no reason??

This. But I found the New Vegas map to be way more interesting. With more unique items and more interesting characters.

I think the New Vegas map is smaller and also has unreachable areas.

Really?? I found the FO3 map to have more spots of interest. I mean they both have tons of places to visit, but I felt like they were more interesting in FO3. But I've only played through NV once.