Scath or Tamalancer

Why would you want to burn a 5*... ... ...

Scathach is Boss killer usually due to Her +Quick and anti divine/undead skill. Her only con is bad NP regen. Unless you got some support tthat can help charge NP sometime she die without using NP.
Tama-chan is one of best anti-male. Her NP also charge fast. But her skill make it tricky to use. Best bring a debuffer to help her. Technically both is good civilization

Burn them both for rare prisms.

You must be very desperate if you are burning 5*

Why not both?

There's no limitation on burning servants and two prisms is twice as many as one...

Winning!

You could, you could do that... But why would you

I see you're a man of culture.
Why not both though?

as some one that no have any gold lancer I can say you that they are not necessary, Cu FSN and Cu Proto can make the work very well, just burn both.