Question Case with only one fan option question

[spanolo]

Guys, my dad has one of those micro cases with only one fan placement option on the back for 80mm fan.

I have a spare fan, so should I make that one exhaust or intake one?

 

[Dj0gany]

What case does he have?

 

[spanolo]

Some generic brand, I couldn't even find it on Google...

As I said, basic mini tower, it has only one 80mm fan placement on the back, right under PSU, and one side odf the case has hole openings for air, without filter...

It's pretty low end configuration also, APU with stock coller, and current temps are alright, but I just want to give that spare fan a function...

I know that rear fans are considered exhaust ones, but would it have some benefit to make it intake one, maybe less dust?