Definitely the "says nothing" one - I assume this means no smile, no expression, no indication of thought process or intent.
When I know someone I learn what their body language means, and seeing them "smile sweetly" gives me at least a vague idea of what is going on, but if they remain stoically poker-faced, that is when my own creative juices get the better of me, painting all kinds of pictures in my mind. It is truly terrifying!
On a personal note, there is this mental state, and meditation technique employed when one has to perform at a level beyond speed of thought, involving freeing of doubt, hesitation, and pesky interference from conscious thought into what is instinct, trained action, muscle memory. This is something I practiced many times with a mentor who was very big on mental imagery. This particular state of free-floating action - free from fear - is what was reinforced by the mantra "stop thinking, smile sweetly, knowingly" - so you see, I cannot be afraid when someone smiles like that - I smile too and am ready to dance.