My boat and sails are WHITE, the water is SPARKLY/GLAREY, my eyes are SENSITIVE. Therefore, I wear the dark sunglasses. There's no way I can predict how well I'll be able to see something on the boat, so my preference is to make a decision by taking the thing outside, then looking at it through my sunglasses. Don't forget to consider the angle that your gages will be relative to your eyes and whether they will be in sunlight or shaded by a dodger or bimini.