If you are going to shoot something that you believe may wind up on TV, contact the Network engineers and ask what is being accepted. A local producer just sank $35K into a pilot for ESPN and they sent it back as "Unusable. Format not accepted". I know that he shot with a JVC100HD but am not sure what he mastered to. Better to spend a week on the phone finding out before spending a dime on production. The Panasonic Varicam and the Sony F-900 are accepted everywhere. The smaller stuff is still searching for a home. And don't listen to your stupid friends that don't know anything. Get it from the horses mouth, IN WRITING.
Try before you buy, as with any large purchase.
Rent each camera you are considering and see how they actually work, and how the video you shoot looks.
If you have an edit system that will handle HDV or P2, do some tests there as well.