Which fan?

I have a 2400 case and am wondering which kind of fan is better. The 2400 doesnt have space for another case fan so i am considering buying one you just stick into a PCI slot or 5.25 slot (for CD drives). Now i have several questions, should i get one that blows hot air out? or one that just blows air? and if i do get the one that blows hot air out, should i get one for the 5.25 braket? or PCI?(links to the fans at bottom)

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=120565&CatId=0
http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=633877&CatId=0