D600/800: 35mm or 50mm as a first lens?

Hi everyone,

I plan on comparing/handling and ultimately buying either a D600 or D800 in the coming days. Stepping up from a Panasonic GF-1 which I still love using, and which has taught me the power of a good pancake lens.

Looking to spend $500 or less. Would you kindly offer your perspective on whether I should buy a 35mm or 50mm - and which model, specifically?

Thanks so much,

S.