[Canadian Man]

Well with the reactor I thought up for the course it could be either. As to what is bettet the jury is still out to lunch on that one
Some will say down flow some will say up.

-Down flow sometimes suffers from media compaction which isnt a problem with a large enough pump.
-Up flow reactors keep the media nice and loose but because the media grinds together you can get "cloudy reactor syndrome(came up with this term myself!)" which can make your tank cloudy cause of all the little particles of media.