Hi Tim and All,
I have run omnis and subcardioids at Red Rocks quite a bit, but with mixed results. Generally, like has already been said, I find that Omnis will be boomy if run with a substantial wall or incline behind them (Red Rocks, The Greek, Mud Island).
I hoped subcards would be the ticket to great tapes at Red Rocks but I was only moderately pleased with the DPA 4015's (subs) during the Panic shows last year. Ironically, they were a bit better than the 4011's (cards) which I haven't liked much at the Rocks, but I wish I had run another flavor (I've gotten great results with AKG 480's and MBHO 603 cardioids at Red Rocks). As a major exception to this, I made a really nice recording of Blues Traveller at Red Rocks with Microtech Gefell M296 omnis back in '97.
Tim, since you are nearby, feel free to come by and raid the collection. I have a lot of recordings you could use to aid your decision.
Of course, first hand listening and making your own mistakes or having your own successes is the best way of determining what works best for you.
Happy Recording Everybody,
Marc