If you're looking for one or the other, just choose based on guns vs. magic/swords. Or fantasy vs. sci fi.
They're similar enough to where it won't matter.
Specific differences that stand out:
Fallout has more interesting (and simpler/easier/better) leveling with perks and experience.
Oblivion has more quests and questlines that are far more interesting than anything in Fallout (the Dark Brotherhood quests, Shivering Isles which comes in the GotY edition). While Fallout has more detailed quests, longer and more options to complete.
Ummm. There was more but my monorail of thought (yes, it's a monorail, I'm a modern kind of guy) totally jumped the tracks. xD
Personally, I prefer Oblivion (Shivering Isles is the best Bethesda game I've ever played all by itself). But I can recognize that Fallout 3 did a lot of stuff better than Oblivion (leveling, random events, graphics, fighting mechanics).
NOTE: I also don't have any opinion on the PS3 version, because I have only played these games on 360 and PC.
They're similar enough to where it won't matter.
Specific differences that stand out:
Fallout has more interesting (and simpler/easier/better) leveling with perks and experience.
Oblivion has more quests and questlines that are far more interesting than anything in Fallout (the Dark Brotherhood quests, Shivering Isles which comes in the GotY edition). While Fallout has more detailed quests, longer and more options to complete.
Ummm. There was more but my monorail of thought (yes, it's a monorail, I'm a modern kind of guy) totally jumped the tracks. xD
Personally, I prefer Oblivion (Shivering Isles is the best Bethesda game I've ever played all by itself). But I can recognize that Fallout 3 did a lot of stuff better than Oblivion (leveling, random events, graphics, fighting mechanics).
NOTE: I also don't have any opinion on the PS3 version, because I have only played these games on 360 and PC.