Black candy

What is the difference between these two?
The shape? No. Well, that is not what I mean.
The colour? No. Well, that is not what I mean.
The sugar on the one on the right? No. Well, that is not what I mean.

These are two typical very Finnish sweets.
The one on the left is salmiak.
The one on the right is tar candy pastilles.
Salmiak is good.
The other is not.
That is the difference, the taste.
Guess which one is my favourite?

And no, the tar candy do not contain tar. They are completely harmless to eat.
The salmiak candy have a history.