That depends soley on what your needs and wants are. Aluminum is alot lighter than steel. The amount of fans will vary, thus, keeping your case cooler/hotter. There are alot more variations to consider such as HDD bays, how many, which way they face, etc. For reviews on cases check out www.tomshardware.com and search for reviews on cases. To look into buying one, i recommend www.newegg.com. Best of luck.
refer to pervious post by randruff. it depends on what you want. lian-li's aren''t "flashy" or anything, but damn they are expensive. i love the flat black look.