[pkautzsch]

No baffle: just personal taste.
I prefer larger spacing between the mics since this doesn't add L-R color differences and makes the sound wider and more spacious. Baffles seem a bit risky to me since reflections can produce comb-filterish sound (it's similar to placing a mic a few inches from a wall, isn't it). The omni pair in your case is more like a room mic to add richness and volume, and space. The wider you space the mics, the more spacious it will sound.
Pressure transducers (SDC omnis - probably the Avensons?) will have the best bass response.