A case may be judged on things such as:
1) Form factor (category)
2) Motherboard compatability
3) number of hard drive slots
4) number of expansion bays
5) does it include the latest tehnology
6) Could almost anybody know how to use it (simplicity)
7) cooling capabilities
I would create a spread sheet and rank all of the cases based on each category. Then give 1 point to a 3rd place, 2 points to a 2nd place, and 3 points to a 1st place standing. Then I will tally up the points for each case and then rank them based on which one's have the most points. More points is better.
Getting a spot in the top 5 of a category confers bragging rights to the company that made that piece of hardware and get my seal of approval as a quality piece of hardware.