Is BlackGlasses A Better Choice Than A Dark Gem?

Question

I need one for my Scraggy but which is a better choice?

Answer 1

Let's look at what both do.

BlackGlasses: (You called them Dark Sunglasses)
20% Increase in power on all Dark Type Moves.
Can be used on all dark moves a Pokemon has.
Non-Consumable

Dark Gem:
30% Increase in power on 1 Dark Type Move. (50% in Black, White, Black 2 and White 2)
Can only be used once.
Consumable

From the information above, I would recommend BlackGlasses over Dark Gem, as you will see more use out of the BlackGlasses.

BlackGlasses | Dark Gem