Case Fan Setup?

[nikbear]

I have a Thermaltake M5 case which has a 14cm induction fan at the front,a 14cm fan in the top for exhaust as well as a 12cm in the back.
There's room in the side panel for 2x12cm fans,but,....and here's my dilema,should they be exhaust or intake Whats the considered opinion on this

 

[nikbear]

Thanks for the suggestions,I will experiment and see how I get on