Suppose that sunlight falls both on a pair of reading glasses and on a pair of dark sunglasses. Which pair of glasses would you expect to become warmer?
Almost all sunglasses are made dark by adding an absorbing material to the glass or plastic. Most of the sunlight's energy is converted to heat going through that absorbing material.
Knowing that, what do you think the correct answer is?
then it has to be reading glasses.
Here is a bit more information that might interest you. I still stand by my previous answer.
Polarizing sunglasses also absorb about 75% of the light going through, regardless of how the incoming light is is polarized. It is possbile to make sunglasses with a dielectic reflective coating that does not absorb light, but it would more expensive to make them that way, and the mirrorlike appearance when seen from the front would be somewhat annoying. Most reflective sunglasses use a partially transmitting metal coating, which does absorb light.