If you are displaying a table of data, use <table>. <div> grids don't paste well into Excel. Tables really aren't evil, they are a better fit for many tasks where you effectively need a table and can generate the data in row order. Nested tables can be pretty evil. Go with a div grid if you feel the even the hint of wanting to nest.

See the triumph of KML (which mixes content and presentation) over straight GML (separate content and presentation) in the GIS world for comparison.