Well, it is more on the opinion of which you were taught to use. Both have their standards, and there is a difference between Tables and CSS.
Tables belong in the HTML 4.x specs (I dont believe the HTML 2.x spec had tables) and CSS has it own. They are two different things.
CSS is used to modify certain objects (like an overlay, as it needs html to show itself), and its main purpose was to create a way to make one page have several different uses for display (i.e on projectors, the www, and monitors).
Tables are for formatting and seperating content into their own cells, and are real good at it. Now, you have two choices, tables or divisions (i.e divs).. divs are more flexible, and css can be used a lot more effeciently with div's then tables.
My suggestion, use what you know how to use, or if you are a code junky like me, use the one you don't have a clue about and learn how to use it..
If this is too much of an explaination, sorry.. however I think it needed to be clarified..