I think omnis in a NOS looking setup would sound great.
- I listen with earbuds/headphones a lot, and too much split doesn't please me. I think 12" is probably a good compromise between DINish and wide-splits.
- Omnis will pick up more chatter around you if there is the typical crowd... that's a fact of life. A little chatter is OK, but too much really pisses me off.
I'm conservative by nature. I would probably run that way for some of the of the opening acts (the ones that I might not get around to tracking anyway), and then "go with what you know" (in my case cards/DIN) for the main acts, just in case it didn't work out as well as I had hoped. Also, a lot of festival fields are "half full" during the day, and then are "really packed" when the main acts come on at night, which is when the chatter factor increases.