Re: psu question
Besides styles you have to consider things like good air flow, materials and quality of construction, sufficient room inside for those planning to use liquid cooling setups, and other reasons as well. The case here is an Antec 900 model seeing twin 120mm front intake fans while the next person to come along may have the NZXT Guardian seeing an lcd monitor on top for cpu temps, voltages, etc. there.
One style will see one large door or two swing to the side doors for covering the 5.25" drive bays in front. One case will see front audio input/head phone jacks, usb, and even eSata ports on the front panel while another sees those on top or not at all.
As for materials many are made of aluminum and plastic with most cases seeing a plastic face plate to start with while most prefer a steel with plastic. Each brand and style often sees something at least slightly different explaining the various price ranges.