It depends.

If the larger tube fit well in my tire without appearing to wrinkle or kink then I'd probably go with that. As terrymorse said it'll lose air more slowly when punctured generally, not every time. But on the other side of that, a smaller tube that is stretched to fill up the inside of the tire is going to behave more like a balloon being stuck with a pin when punctured.

When I had my last flat I was able to ride the bike home for five or six miles as the leak was slow so I just kept topping it off with air a couple times. Changing a flat in the comfort of AC is more desirable than changing a flat in 90°F and 90% humidity.