Here is John Loftus arguing that the size of the universe points to atheism. This wunderkind of atheistic apologetics actually writes this concerning the size of the universe:
I think it's even more damaging when it comes to an omnipotent God who supposedly created the universe for the specific purpose of gaining the affections of people on this lone planet of ours. If this is what he desired (for some irrational egotistical reason) he could have simply created us on a flat disk in a much smaller universe like the one the ancients believed existed.The worst argument for anything is "if I were God, this is what I'd do." It's dumb when Christians use it--and fundamentalists tend to use it a lot. And it's dumb when atheists use it.
There are at least two arguments for the vastness of the universe.
1) God just felt like doing it. (Not satisfying, but it can't be ruled out by saying but I'd do it differently if I were God!)
2) God turned the evolution of the universe over very early to secondary causes (physics) and there is plausibly a connection: habitability → galaxies → constraint on the initial baryon density of the universe → large universe.
Intellectual atheism in the 21st century:
• If God made everything, who made God? (Dawkins)
• Religion poisons everything! (Hitchens)
• Science and religion are not compatible! (Coyne)
• I'm a genius and can use Bayes's Theorem to show Jesus didn't exist! (Carrier)
• Menz suck! Theists is dumb! (Myers)
• If I were god, I'd make a small universe, ergo no god! (Loftus)