I think this is a very good question, and both sides have valid points.
I am a Percussion Judge, and I feel that the judge should be on the field if there is one judge. In a perfect world, there would be a field guy and a box guy (or gal lol) but that won't happen. Judging in the box is good if you are a) in a small stadium, and B) if the band your are adjudicating isn't too large. What I mean by the too large comment is, for example in Florida, if you are judging Cypress Creek HS, with over 150+ wind players and usually writes the drumline behind the band, it is hard to hear exactly what the battery is playing, so you almost have to go on the field even if it is a little bit to get a sampling for what is going on back there. I have viewed them from the box and the sound just gets lost in the thickness of the wind sound. But, I see what people mean when they feel that a judge that goes back in the back with the battery misses a lot of stuff---and if they stay back there too long they will. I try to stay up on the track where I can sample the whole program, and I can usually do a good job catching everything...I don't go onto the field too much and when I do I try not to go all the way back unless necessary--and when I do, I am not back for too long. This way I can get a sense for what the ensemble is doing as a whole. Also, if the judge is worth his salt, he will be able to pick up ensemble and balance problems, FOR THE MOST PART, from the sideline. This of course isn't a perfect system, but it has worked for me and it works for DCI as well. Hope this helps...
Jeremy Vest
www.chsdrumline.com
PS-In a perfect world though, the Percussion Caption would have 2 judges lol...would be nice. And I also feel the judge should have sufficient knowledge of battery and front ensemble percussion.