Which kit lens for OM-D

Hi,

I am going to pull the trigger on a OM-D soon. Can the forum members help me to understand the differences and virtues between the two kit lens options? I am struggling to decide which kit lens to order. The 12-50 seems to be about twice the size of the 14-42, I want am switching to M43 to keep my kit as portable as possible, but wondering what the tradeoff is.

Thanks!