Trying to Choose New Camera and Lenses: Sony NEX vs Olympus OM-D

Many thanks for the quick reply! Very helpful indeed and I feel encouraged that I am at least partly on the right track in terms of thinking! Regarding external flash options, I have still not understood whether the NEX6 requires specific Sony (or Minolta) accessories or is universally compatible with a multitude of third party stuff? Any input on this also much appreciated! Thanks!