I would think the omni would give you more sence of the veue, more crowd more sence of space, if the venue didn't have an echo I don't think the omni would create one, Just my take on the sound an omni produces, to the other side of this Yes if the room was boomy or had an echo the omini would most likely aplify that because the wider pattern than say the cards. When speaking in terms of cards I don't see the benifit of having 2 sets running at once and being mixed down to 2 channels, I am very happy runnig 1 set of mics, ease of set up and less to worry about, all though I have been thinking of getting omni caps for my octavas and running them split a couple of feet with the lsd2 running x/y cards center and mixing it all down w/ the ua-5. Just not sure if there is any advantages, and so far the lsd2 sounds great by itself, don't want to mess that up.
Shayne