Common chambers are perhaps the most common style of chamber found on hookahs, these are found almost exclusively on chinese style hookahs, which just so happen to be the most readily available hookahs on the market. Because of the shared airspace of the hose port and purge valve being in the chamber rather than in the base of the hookah common chambers make it literally impossible to purge smoke in the base of the hookah, witch obviously is where the majority of the smoke is held. The reason for their inability to purge is because instead of the air flowing through the base where the smoke is held it merely travels across the metal chamber and out the purge port leaving the smoke in the vase untouched.
Traditional chambers are found on a wide verity of hookahs, though they are much less common in terms of availability, especially in the states. Traditional style chambers are most commonly found on Egyptian hookahs, but are not uncommon on syrian and lebanese hookahs. Traditional chambers are noted as being the best kind of chamber not only because they allow for all of the smoke to be cleared out of the vase but also because they are much easier to clean, though they do require a brush of some kind to be cleaned. The reason these kind of chambers work so well is because of a shared air space in the chamber its self they have a tube that runs from the hose port and purge valve to the bottom of chamber. The air space is thus shared in the vase rather than the chamber and allows for all the smoke to be purged from the vase.
Lack Of A Purge Valve
Some hookahs lack a purge, but to be honest this is not a common thing to see on most hookahs, this is something that is mainly seen on turkish or lebanese hookahs. This is basically self explanatory, you have no ability to purge because there is no valve with which to purge with. It comes down to they way the turkish smoke, the way they see it, if you cant manage your heat well you shouldn't be smoking.
Below are a few pictures of chambers from a number of common brands on the market so that you can distinguish between chamber designs just by looking at the bottom of the chamber.
Open Common Chamber
Most commonly found on Mya Saray Hookahs, witch are considered top of the line as far as chinese hookahs go. The main advantage to this type of chamber is that it can be easily cleaned and if necessary they can be modified to purge.
Plated Common Chambers
These are the more commonly found chambers on chinese pipes and the kind of chamber that I have on both of my chinese rigs. They are literally impossible to clean out. The most recognizable trait of these chambers is that they have more holes than ports usually. They normally have 4 or more holes on the bottom.
These chambers are considered the best purging chambers and are mainly found on Egyptian hookahs and on some syrian and Lebanese hookahs. They have the same number of hoses on the bottom of the stem as there are ports on the hookah. This normally means that there are two holes as most egyptian hookahs have only one hose port and one purge.
Hopefully this post has been helpful. I should have a new section on identifying different hookah styles and their advantages sometime late this weekend. Stay tuned.