If running 4ch is plausible then go ahead and do that if you want. But if you were to choose one or the other, I would personally go with cards due to the reasons above(crowd, somewhat quiet show). In my personal experience, I find a lot of places "acoustically designed for best sound" really don't sound all that good, especially in regards to cards vs omnis. It's possible the omnis pick up quite a bit of roomy sound, but it's all subjective.