Guys...be nice :D
Ok, question..for gocitygo..
1. What sub are you using? Do you have a specific model in mind?
2. For general difference, you can search the web, for specific difference, use winisd software to model an enclosure for you. Select the sub model you have/plan to have, and choose the enclosure, from there you can see and adjust the sub enclosure to suit your taste.
Please take note that some sub are specifically designed to perform in certain enclosure. Only some exceptional few are good sub that can perform in any enclosure type. So, the best idea is to follow the manufacturer's recommended sub enclosure type. Because they normally know's best what their sub can do. :D peace