How To Lock Your Bike

Is it better to use a small U lock, like the new yorker, or a larger one. I'd assume the smaller one so there is less space for leverage?

Use one that is big enough to fit around your frame, a wheel and a stationary object in the street. Anything larger is unecessarily heavy.

Strength wise size makes little difference, it will not affect cutting. But a smaller lock will make it harder to get a jack in it.