To my ear omnis sound really "unnatural" if you're not close to the sound source. Maybe they sound too "natural" that they lose their musicality but without proximity effect going on you just end up with this airy kind of thin feeling sound. Really if you're far enough out from the source that you can start to hear any sort of ambient noise (cars, chatter, babies crying...) the omnis aren't going to catch all of that too. Running the mics at 180 isn't going to do anything for omnis besides distancing the capsules since they have a spherical pickup pattern. If you really wanted to you could point them towards the sun and it wouldn't matter.
All of this talk about particular distances and measurements blah blah blah, just bring headphones and configure the mics in a way that sounds good to your ears. Every show is going to have unique acoustics going on so you have to measure with your ears. Not trying to be sassy it's just how it is. You can have all the formulas you want but you must always abide by the golden rule of recording, turd sound in = turd sound out.
For the sake of simplicity, it would be great if generalities hold enough truth to be useful in discussions like this, unfortunately in the real world there is little truth in such generalities.
Unless tempered with conditional considerations, generalities tend to give misleading mis-information educating only the
indiscriminate majority.
What IS true is NOT ALL OMNIS sound the same in the same situation for many reasons, and NOT ALL BAFFLES sound the same for many reasons in the same venue position.
The reasons for this might fill a few volumes or
simply be understood with saying the
acoustics is different with each make of omni mic and baffle construction.
Therefore, your results will vary all over the map from
'excellent to piss-poor' depending on
which omni and
what kind of baffle construction is being used
independent of mic position within the venue.
Now you've heard
some real truth about omni's and baffles, but maybe not so useful or what you where hoping to hear.