Up until recently, I've recorded all gang vocals with multiple passes with varying positions around a single omnidirectional microphone (Avantone CV12)... this has worked well, and with varying degrees of pan, reverb, compression, you get a very convincing 'small crowd' sound.
I've heard a lot of fuss about mid/side and blumlein techniques for this - my question is - have you recorded gang/chant vox (or even simulated choir) with these techniques successfully? What are the upsides/downsides?