Yep, what Lil Kim said.
And for that matter, even if there was to be an audible difference, what you heard is backwards. Larger conductors have less resistance, and less resistance means more of the signal gets through. So the larger cables would be theoretically louder and easier to push, not the other way around. Think about speaker cables -- small diameter zip wire is considered bad, and large, garden-hose size speaker cables are the bomb.