Etched is the strongest.
But as all glasssurfaces steals ligth, a glass reticle steals with the best coatings availible 0,5% light and with no coating 8% light.
0,5% is in my opinion not visiable, but 8% is for sure.
Many years ago one of the magazines here had a test betwen various of the best 8x56 scopes to see wish one was the brigthest, they was both looked thorugh and measured.
Swarovski loosed by fairly big margin and that was explained mostly due to their glass reticle, but that can't be only that, as the percentage differed to much.
Regards Technika