Oblivion felt more clunky and unrealistic. While it is from the same designer, the immersion that I love in Fallout isn't really present in Oblivion. I'm sure I'll keep playing it since I did pay for it, but it feels more like a game where F3 feels more like a journey, and while games are great, journeys are better in my mind
Oblivion is by no means a bad game, but it's easy to tell that it came before F3. That kind of makes it an unfair comparison for that reason, Obliv. was the first try, and the things they fixed helped make F3 better