Brian, i like the idea but i might suggest that rather than talking meta genre vs. meta genre, that we pit the sub genre vs sub genre. i.e. one night we do "classical" and set the moderns against the classical vs baroque vs opera (although not a period) vs medieval etc. (or whatever)

A jazz night might include various sub classifications that might be geographical or by era or stylistic distinctions ...or maybe a showdown of the best jazz instrument.

I found that the last battle we did was fun but too polarizing and i think that pitting classical vs disco is just not fair because they are such different beasts. (although i am sure the disco would emerge triumphant)

With rock you could mix it up and send the "trio" into the ring against the "ballad" or the "glam icon" or whatever. I like to think it might be a little more interesting and there might even be some disagreement as to whether a particular cut should be allowed to fall into it's category.

Like Stuart, i always like the shades of grey that fall between the black and the white.