I've found that screw on bases tend to break easily and i've never found any advantage in terms of cleaning as vases are the easiest part of a narghile to clean. I've found screw on vases to be thin and poorly made for the most part.
I've also found that it's common for vendors (the less worthy ones at least ) to call a rig Egyptian or Syrian when it's just a piece of shinny crap from China.
I think that in terms of style we should remember that in Egypt spun metal work is far more common then in Syria where cast and machined parts are used in conjunction with fewer spun parts.
We should also keep in mind the head configuration and bowl differences between traditional Syrians ( see www.furathookahs.com
for examples) from the far more common Egyptian style head designs.
It seems that Syrian, Lebanese and Iranian narghiles are stylistically and structurally the same for the most part save the following exceptions:
1) Lebanese and Iranian narghiles tend to use decorative wood and glass on the outer surface of the stem far more then do the Syrians.
2) Lebanese and Iranian narghiles tend to have highly decorative painting on the vase and stems rather then etchings seen on Syrian rigs.