I think they are about the same in difficulty.
Exoddus is longer than Oddysee, with harder puzzles and sequences. But Exoddus has the quicksave feature that makes the game as easy to complete as Oddysee in my opinion, because it means that some really difficult bits to do, you only ever have to do once.
If Exoddus didn't have the quicksave feature, it would be far harder and far more frustrating than Oddysee, in my opinion.
With Oddysee though, it is (or seems) very very difficult and long on the first time you complete it, but as you complete it multiple times (as I have), it doesn't seem so long nor difficult.
So in conclusion, I think that both games are similar in difficulty, but different in the way that they are difficult, which is good.
