@4711, thats true - but i don't want to make "scientific" tests. Thats no more fun for me.
I did some more comparisons shots i do not intend to show here because this type of posting gets fast boring.
My findings and verdict will not surprise anybody:
In IQ the Sigma beats all of my other gear by quite a margin. It makes not to much sense to do a "ranking list", all of the other cams (i have to many...) have their strengths and weaknesses.
Since the Sigmas, i am using them 85% or even more, the rest sits on the shelve.
Depending on what you want to shoot, one Sigma (2 or 3) and the OMD with 12-35 and 75/1.8 or Pana 7-14 + Olympus flash , all fits in a pretty small bag and is not to heavy, is a very good basic set.
I like the NEX 7 as well (think the IQ of the NEX7 is a little superior of the OMD) but the lenses and the whole system gives me not the flexibility of the OMD.