They both have an element of privileging the hypothesis. If I had some reason to think I lived in a universe with an Omega/God then I might agree I should one-box/believe in god but since I don't have any reason to think I live in such a universe why am I wasting my time even considering this particular implausible scenario?
I see what you mean, but there exists one of two problems with the symmetry.
First, the most annoying form of Pascal's Wager is the epistemological version: "Believing that God exists has positive expected utility, so you should do so". This argument fails logically, for reasons SilasBarta listed, and it is usually this form being refuted when people say, "Pascal's Wager fails".
Second, the form of Pascal's Wager concerning worship, "Believing in God, who is known to exist, has positive utility", has moral complexities which are...
It has been claimed on this site that the fundamental question of rationality is "What do you believe, and why do you believe it?".
A good question it is, but I claim there is another of equal importance. I ask you, Less Wrong...
What are you doing?
And why are you doing it?