There is no consequential difference, other than color, between the black or translucent silicone-- as long as they are the same product, ie covered by the same MSDS and Product data sheet. There is no cost difference for the product either. The black is no more difficult to apply than the translucent. I am certain you have seen pictures of tanks with black silicone. WYSIWYG. If not, visit the Elos website. I like the black silicone, some don't.
The difference is in the eye of the beholder. I leave the rest to you.
What is more important than the color is the grade of the silicone ("professional" "industrial" vs consumer grade) and whether or not it is toxic.
Jim