DSLR or Mirrorless - can four third lenses be as good?

Hi,
I am planning to buy a digital camera mostly for portraits. Checking the measurements in dxomark.com I found that D600 has one of the best specifications for the price. On the other hand I really like Panasonic Lumix GH3 for its specs, IQ and video capabilities.

I can save some money on GH3 but my concern is the visual specs of the four third lenses. I can live with a few percent less sensor quality for saving $1,000 but only if I know I will have one or two very good lenses for my GH3. Searching in the Internet, I have seen a few articles saying that 4/3 lenses can actually provide very good MTFs with high quality visuals/sharpness/contrast especially on the edges but quality is relative and I couldn't find any real world comparison between the 4/3 lenses and the Canon or Nikkor lenses.

Obviously such a comparison should have the price in consideration. For example for a budget of under $500, comparing a standard Nikkor zoom (or a normal prime) with almost the same type in four thirds.

Your feedback is greatly appreciated.