PSU Fan location

[General Tso]

I'm down to my final decisions now and am confused about PSU designs. When would I want the PSU's fan to be on the top and when would I want it to be on the bottom? Here's the same PSU, only difference is the fan location:
http://www.newegg.com/Product/Prod [...] 6817182072
http://www.newegg.com/Product/Prod [...] 6817182070

Presumably, it would have something to do with my case selection, but there is no info about it. Just ATX, which it is. Anyway, here's my case:
http://www.newegg.com/Product/Prod [...] 6811112121

 

[Mondoman]

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