Team 1108 has used a PVC-framed pit since I've been with, and it's really just fine. The upper panels are kept assembled with the screen-printed banners in them, while the sides and legs are just stuck-into the fittings and zip-tied through drilled holes.
This year at championships we did switch the back-top bar to EMT to give it enough strength to hold a projector, but generally, it's all made from 2" PVC.
We have to repaint it fairly regularly, but I expect that would be the same for painted metal.
And it does sag a little across a ten-foot span. We keep a set of eight-foot tubes to use in case we go to a smaller event without the normal pit space.
Here's a pic of it partially assembled so you can get the gist:
https://www.facebook.com/media/set/?...type=3&theater
Here was at champs with the projection image:
https://www.facebook.com/media/set/?...type=3&theater
The structure is only for presentation--it doesn't actually include any storage or functionality. I've considered adding LED lighting (pre-wired) to it inside the tubes, but we already have lights that raise up from our tool box.
Whatever you do, just remember people will look at it and associate your team with it. Do something you're comfortable with.