Re: Does it matter?
you will notice a slight difference between an 11 inch hookah and a 60 inch hookah. i noticed the smoke seems to be a bit smoother on my 32 from my 18 but not a lot. i notice though that the size of the vase is a larger factor, a hookah whos base is very large (above the water line) has a bit thicker/more consistent smoke and is not as choppy when you inhale on it (usually you stop noticing this choppyness after a few smokes but it is there).
i put more into the vase size than the stem size, given a longer stem down have more time for the smoke to cool but a bigger thing is that the heat from the coal doesnt travel down as far. on my mya mini half way down the stem gets warm by the time im done where as on a larger rig much more distance is still cool so the smoke can be cooled a touch and the heat wont transfer to the water as much.
buy a quality rig that looks good to you, has a reasonable size for you (if you travel with it a smaller one is smarter, where as if it never leaves your house a larger one may be nicer), etc